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Calculated Shard: 5 (from laksa181)

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curl -X POST \
  'http://laksa005.int.ahrefs:8124/' \
  -H 'Content-Type: text/plain' \
  -H 'X-ClickHouse-Database: crawler3' \
  -H 'Authorization: Basic YXBpOg==' \
  -d 'SELECT getAhrefsURLFromUnparsed(src_unparsed) AS found_url, ifNull(toUnixTimestamp(download_stamp), 0) AS crawl_time, ifNull(toUnixTimestamp(props_url_first_seen), 0) AS first_indexed_time, download_http_code AS http_code, src_unparsed AS src_unparsed, src_root_hash AS src_root_hash, history_drop_reason AS history_drop_reason, meta_title AS meta_title, meta_descriptions AS meta_descriptions, attrs_boilerpipe_text AS attrs_boilerpipe_text, attrs_markdown AS attrs_markdown, attrs_readable_markdown AS attrs_readable_markdown, meta_canonical AS meta_canonical FROM crawler3.page_info_local FINAL PREWHERE (src_root_hash, src_unparsed) IN ((getAhrefsRootHashFromUnparsed(getAhrefsUnparsedNoserviceFromURL(\'https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm","crawl_time":1774131502,"first_indexed_time":1609570455,"http_code":200,"src_unparsed":"gov,cdc!www,\/mmwr\/volumes\/69\/wr\/mm695152a3.htm s443","src_root_hash":"17308952984333333205","history_drop_reason":null,"meta_title":"Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020 | MMWR","meta_descriptions":["This report describes the performance of COVID-19 antigen–based tests for asymptomatic and symptomatic persons at two universities.","This report describes the performance of COVID-19 antigen–based tests for asymptomatic and symptomatic persons at two universities."],"attrs_boilerpipe_text":"Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020\nWeekly\n\/ January 1, 2021 \/ 69(5152);1642–1647\nPlease note:\nThis report has been corrected.\nIan W. Pray, PhD\n1\n,2\n,3,\n*; Laura Ford, PhD\n1\n,2,\n*; Devlin Cole, MD\n3\n,4\n; Christine Lee, PhD\n1\n,5\n; John Paul Bigouette, PhD\n1\n,2\n; Glen R. Abedi, MPH\n1\n; Dena Bushman, MSN, MPH\n1\n,2\n; Miranda J. Delahoy, PhD\n1\n,2\n; Dustin Currie, PhD\n1\n,2\n; Blake Cherney, MS\n1\n; Marie Kirby, PhD\n1\n; Geroncio Fajardo, MD\n1\n; Motria Caudill, PhD\n1\n,6\n; Kimberly Langolf, MS\n7\n; Juliana Kahrs, MS\n7\n; Patrick Kelly, MD\n4\n,8\n; Collin Pitts, MD\n4\n,8\n; Ailam Lim, PhD\n9\n; Nicole Aulik, PhD\n9\n; Azaibi Tamin, PhD\n1\n; Jennifer L. Harcourt, PhD\n1\n; Krista Queen, PhD\n1\n; Jing Zhang, PhD\n1\n; Brett Whitaker, PhD\n1\n; Hannah Browne\n1\n; Magdalena Medrzycki, PhD\n1\n; Patricia Shewmaker, PhD\n1\n; Jennifer Folster, PhD\n1\n; Bettina Bankamp, PhD\n1\n; Michael D. Bowen, PhD\n1\n; Natalie J. Thornburg, PhD\n1\n; Kimberly Goffard, MBA\n10\n; Brandi Limbago, PhD\n1\n; Allen Bateman, PhD\n7\n,11\n; Jacqueline E. Tate, PhD\n1\n; Douglas Gieryn\n10\n; Hannah L. Kirking, MD\n1\n; Ryan Westergaard, MD, PhD\n3\n,4\n; Marie Killerby, VetMB\n1\n; CDC COVID-19 Surge Laboratory Group (\nView author affiliations\n)\nView suggested citation\nSummary\nWhat is already known about this topic?\nAntigen tests for SARS-CoV-2 are inexpensive and can return results within 15 minutes, but test performance data in asymptomatic and symptomatic persons are limited.\nWhat is added by this report?\nCompared with real-time reverse transcription–polymerase chain reaction (RT-PCR) testing, the Sofia antigen test had a sensitivity of 80.0% and specificity of 98.9% among symptomatic persons; accuracy was lower (sensitivity 41.2% and specificity 98.4%) when used for screening of asymptomatic persons.\nWhat are the implications for public health practice?\nTo account for reduced antigen test accuracy, confirmatory testing with a nucleic acid amplification test (e.g., RT-PCR) should be considered after negative antigen test results in symptomatic persons and positive antigen test results in asymptomatic persons.\nAltmetric:\nMendeley (295)\nDiscussion\nThe Sofia SARS Antigen FIA received FDA EUA on May 8, 2020, for use in symptomatic persons within 5 days of symptom onset (\n2\n). In this investigation, among persons reporting COVID-19–compatible symptoms at specimen collection, the test was less accurate (sensitivity = 80.0%; specificity = 98.9%) than reported in the FDA EUA (sensitivity = 96.7%; specificity = 100%) (\n2\n). Two of eight specimens from symptomatic persons that had false-negative antigen test results were positive by viral culture, indicating that potentially infectious persons might not be detected by antigen testing. To reduce the impact of false-negative antigen test results, confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, should be considered following negative antigen test results in symptomatic persons (\n1\n).\nAmong asymptomatic participants, antigen test sensitivity was 41.2%, specificity was 98.4%, and PPV in this population was 33.3%. This low PPV was observed despite a relatively high prevalence of SARS-CoV-2 in this population (5.2% prevalence overall; 2.0% among asymptomatic persons), suggesting that PPV could be even lower when using this antigen test among populations with lower expected SARS-CoV-2 prevalence. To account for false-positive results when using antigen tests for asymptomatic screening, confirmatory NAAT testing should be considered following positive antigen test results in asymptomatic persons, particularly when pretest probability of SARS-CoV-2 infection is low (\n1\n). The NPV of antigen testing among asymptomatic participants was 98.8%, and virus was not cultured from asymptomatic participants with antigen-negative results, indicating that asymptomatic persons with negative antigen results are unlikely to be infected with SARS-CoV-2 and would not require confirmatory NAAT (\n1\n).\nThe findings in this report are subject to at least four limitations. First, participants were predominantly young adults in university settings where ongoing serial testing was being conducted. Antigen test performance might differ in other populations with different characteristics and testing schedules. Second, given the limitations of RT-PCR, some false-positive antigen test results might represent true infections not identified by RT-PCR. Third, the ability to recover infectious virus in culture is limited and decreases for specimens with higher Ct values (\n8\n); a lack of virus recovery by culture does not indicate that a person is not infectious. Finally, this investigation evaluated the Sofia SARS Antigen FIA, and cannot be generalized to other FDA-authorized SARS-CoV-2 antigen tests.\nSerial testing of asymptomatic and symptomatic persons has been proposed for prevention and control of SARS-CoV-2 transmission (\n9\n,\n10\n) and is currently being implemented at U.S. colleges and universities and in other congregate settings (\n3\n–\n5\n). Despite reduced sensitivity compared with real-time RT-PCR, the use of antigen tests for serial testing in these settings, particularly when RT-PCR tests are not available or have a prolonged turnaround time, might still allow rapid identification of infectious persons and control of outbreaks (\n1\n). However, antigen-based testing strategies should account for the lower sensitivity and lower PPV when used for asymptomatic screening by considering confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, after a positive antigen test result in an asymptomatic person. Confirmatory testing should also be considered following a negative antigen test result in a person experiencing COVID-19–compatible symptoms. All persons with negative antigen test results should continue to take measures to prevent SARS-CoV-2 transmission, including wearing a mask, reducing contact with nonhousehold members, and getting tested if they experience symptoms or have close contact with someone who has COVID-19.\n†††\nSymptomatic persons with negative antigen test results should continue to follow CDC guidance\n§§§\nfor persons who might have COVID-19, including staying home except to get medical care and protecting household members by staying in a separate room, wearing a mask indoors, washing hands often, and frequently disinfecting surfaces.\nAcknowledgments\nEdward Samuel Rivera, Daniel J. O’Donnell, University of Wisconsin-Oshkosh; Margaret Okomo-Adhiambo, Umesh Parashar, Paul Rota, Lauren Franco, Gerardo Garcia-Lerma, CDC; Neeti Dahal, Wisconsin Veterinary Diagnostic Laboratory-Wisconsin State Laboratory of Hygiene COVID Laboratory, University of Wisconsin-Madison.\nCDC COVID-19 Surge Laboratory Group\nBaoming Jiang, CDC; Jan Vinjé, CDC; Amy L. Hopkins, CDC; Eric Katz, CDC; Leslie Barclay, CDC; Mathew Esona, CDC; Rashi Gautam, CDC; Slavica Mijatovic-Rustempasic, CDC; Sung-Sil Moon, CDC; Theresa Bessey, CDC; Preeti Chhabra, CDC; Sarah L. Smart, CDC; Raydel Anderson, CDC; Kay W. Radford, CDC; Gimin Kim, CDC; Dexter Thompson, CDC; Congrong Miao, CDC; Min-hsin Chen, CDC; Lalitha Gade, CDC; Renee Galloway, CDC; Kashif Sahibzada, CDC; Nhien M. Tran, CDC; Srinivasan Velusamy, CDC; HaoQiang Zheng, CDC; Kenny Nguyen, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Claire Hartloge, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Brent Jenkins, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Phili Wong, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee\n1\nCDC COVID-19 Response Team;\n2\nEpidemic Intelligence Service, CDC;\n3\nWisconsin Department of Health Services;\n4\nSchool of Medicine and Public Health, University of Wisconsin-Madison;\n5\nLaboratory Leadership Service, CDC;\n6\nAgency for Toxic Substances and Disease Registry, Atlanta, Georgia;\n7\nUniversity of Wisconsin-Oshkosh;\n8\nUniversity Health Services, University of Wisconsin-Madison;\n9\nWisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison;\n10\nWinnebago County Health Department, Oshkosh, Wisconsin;\n11\nWisconsin State Laboratory of Hygiene.\nAll authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.\n* These authors contributed equally to this report.\n†\nOther affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members.\n§\nSymptom list was based on the interim position statement for COVID-19 case definitions from the Council of State and Territorial Epidemiologists, updated August 7, 2020. Clinical criteria for COVID-19 included fever, cough, shortness of breath, fatigue, sore throat, headache, muscle aches, chills, nasal congestion, difficulty breathing, diarrhea, nausea, vomiting, abdominal pain, rigors, loss of taste, and loss of smell.\nhttps:\/\/cdn.ymaws.com\/www.cste.org\/resource\/resmgr\/ps\/positionstatement2020\/Interim-20-ID-02_COVID-19.pdf\n.\n¶\nRecent exposure was defined as being within 6 feet of a person with a COVID-19 diagnosis for ≥15 minutes in the past 14 days.\n**\nhttps:\/\/www.fda.gov\/media\/137885\/download\n.\n††\nSpecimens were used to perform a limiting-dilution inoculation of Vero CCL-81 cells, and cultures showing evidence of cytopathic effect (CPE) were tested by real-time RT-PCR for the presence of SARS-CoV-2 RNA. Viral recovery was defined as any culture in which the first passage had an N1 Ct at least twofold lower than the corresponding clinical specimen.\n§§\nCt values from real-time RT-PCR were only compared for specimens collected at university A that were analyzed with the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2.\n¶¶\n45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq.\n*** The participant with a false-negative result 2 days after symptom onset had a repeat specimen 2 days later; the results of testing were positive by antigen test and by real-time RT-PCR.\n†††\nhttps:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/prevent-getting-sick\/prevention.html\n.\n§§§\nhttps:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/if-you-are-sick\/steps-when-sick.html\n.\nReferences\nCDC. Coronavirus disease 2019 (COVID-19): interim guidance for antigen testing for SARS-CoV-2. Atlanta, GA: US Department of Health and Human Services, CDC; 2020.\nhttps:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/lab\/resources\/antigen-tests-guidelines.html\nFood and Drug Administration. In vitro diagnostics EUAs. Silver Spring, MD: US Department of Health and Human Services, Food and Drug Administration; 2020.\nhttps:\/\/www.fda.gov\/medical-devices\/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices\/vitro-diagnostics-euas\nCDC. Coronavirus disease 2019 (COVID-19): guidance for testing, screening, and outbreak response for institutions of higher education (IHEs). Atlanta, GA: US Department of Health and Human Services, CDC; 2020.\nhttps:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/community\/colleges-universities\/ihe-testing.html\nCDC. Coronavirus disease 2019 (COVID-19): testing guidelines for nursing homes. Atlanta, GA: US Department of Health and Human Services, CDC; 2020.\nhttps:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/hcp\/nursing-homes-testing.html\nCDC. Coronavirus disease 2019 (COVID-19): interim considerations for SARS-CoV-2 testing in correctional and detention facilities. Atlanta, GA: US Department of Health and Human Services, CDC; 2020.\nhttps:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/community\/correction-detention\/testing.html\nLu X, Wang L, Sakthivel SK, et al. US CDC real-time reverse transcription PCR panel for detection of severe acute respiratory syndrome coronavirus 2. Emerg Infect Dis 2020;26:1654–65.\nCrossRef\nPubMed\nHarcourt J, Tamin A, Lu X, et al. Severe acute respiratory syndrome coronavirus 2 from patient with coronavirus disease, United States. Emerg Infect Dis 2020;26:1266–73.\nCrossRef\nPubMed\nGniazdowski V, Morris CP, Wohl S, et al. Repeat COVID-19 molecular testing: correlation of SARS-CoV-2 culture with molecular assays and cycle thresholds. Clin Infect Dis 2020;ciaa1616.\nCrossRef\nPubMed\nWalke HT, Honein MA, Redfield RR. Preventing and responding to COVID-19 on college campuses. JAMA 2020;324:1727–8.\nCrossRef\nPubMed\nPaltiel AD, Zheng A, Walensky RP. Assessment of SARS-CoV-2 screening strategies to permit the safe reopening of college campuses in the United States. JAMA Netw Open 2020;3:e2016818.\nCrossRef\nPubMed\nTABLE 1. Characteristics and symptoms of persons providing paired nasal swabs (N = 1,098),* by results for SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) and Sofia SARS Antigen Fluorescent Immunoassay testing† — two universities, Wisconsin, September–October 2020\nCharacteristic\nNo (%)\nTrue positives (N = 39)\nFalse negatives (N = 18)\nFalse positives (N = 16)\nTrue negatives (N = 1,025)\nTotal (N = 1,098)\nTesting site\nUniversity A\n§\n37 (94.9)\n17 (94.4)\n15 (93.8)\n982 (95.8)\n1,051 (95.7)\nUniversity B\n¶\n2 (5.1)\n1 (5.6)\n1 (6.3)\n43 (4.2)\n47 (4.3)\nSex\nMale\n16 (41.0)\n9 (50.0)\n12 (75.0)\n416 (40.6)\n453 (41.3)\nFemale\n23 (59.0)\n9 (50.0)\n4 (25.0)\n609 (59.4)\n645 (58.7)\nAge group (yrs)\n15–24**\n35 (89.7)\n16 (88.9)\n11 (68.8)\n909 (88.7)\n971 (88.4)\n≥25\n4 (10.3)\n2 (11.1)\n5 (31.3)\n116 (11.3)\n127 (11.6)\nRace\/Ethnicity\n††\nWhite\n31 (79.5)\n17 (94.4)\n12 (75.0)\n857 (83.6)\n917 (83.5)\nHispanic\/Latino\n6 (15.4)\n0 (0)\n1 (6.3)\n54 (5.3)\n61 (5.6)\nBlack\/African-American\n0 (0)\n1 (5.6)\n2 (12.5)\n26 (2.5)\n29 (2.6)\nAsian\/Pacific Islander\n0 (0)\n0 (0)\n0 (0)\n49 (4.8)\n49 (4.5)\nAmerican Indian\/Alaska Native\n0 (0)\n0 (0)\n0 (0)\n3 (0.3)\n3 (0.3)\nOther\/Unknown\/Multiple races\n2 (5.1)\n0 (0)\n1 (6.3)\n36 (3.5)\n39 (3.6)\nUniversity status\nStudent\n35 (89.7)\n17 (94.4)\n13 (81.3)\n929 (90.6)\n994 (90.5)\nFaculty or staff member\n4 (10.3)\n1 (5.6)\n3 (18.8)\n74 (7.2)\n82 (7.5)\nOther affiliate or unknown\n§§\n0 (0)\n0 (0)\n0 (0)\n22 (2.2)\n22 (2.0)\nExposure\n¶¶\nto a COVID-19 case\nBeen in close contact in the past 14 days\n13 (33.3)\n9 (50.0)\n4 (25.0)\n128 (12.5)\n154 (14.0)\nQuarantine status\nQuarantined at time of specimen collection\n17 (43.6)\n6 (33.3)\n3 (18.8)\n109 (10.6)\n135 (12.3)\nTime between quarantine initiation to specimen collection, median days (range)\n1 (0–8)\n3.5 (0–6)\n1 (0–4)\n4 (0–28)\n4 (0–28)\nReported symptoms\nNo current symptoms\n7 (17.9)\n10 (55.6)\n14 (87.5)\n840 (82.0)\n871 (79.3)\nOne or more symptoms in the past 14 days\n2 (28.6)\n1 (10.0)\n0 (0)\n50 (6.0)\n53 (6.1)\nNo symptoms in the past 14 days\n5 (71.4)\n9 (90.0)\n14 (100.0)\n790 (94.0)\n818 (93.9)\nOne or more current symptoms\n32 (82.1)\n8 (44.4)\n2 (12.5)\n185 (18.0)\n227 (20.7)\nNasal congestion\n24 (75.0)\n2 (25.0)\n1 (50.0)\n87 (47.0)\n114 (50.2)\nSore throat\n12 (37.5)\n5 (62.5)\n1 (50.0)\n79 (42.7)\n97 (42.7)\nHeadache\n17 (53.1)\n3 (37.5)\n1 (50.0)\n66 (35.7)\n87 (38.3)\nCough\n18 (56.3)\n6 (75.0)\n1 (50.0)\n45 (24.3)\n70 (30.8)\nFatigue\n14 (43.8)\n3 (37.5)\n1 (50.0)\n42 (22.7)\n60 (26.4)\nMuscle aches\n11 (34.4)\n2 (25.0)\n0 (0)\n30 (16.2)\n43 (18.9)\nShortness of breath\n7 (21.9)\n1 (12.5)\n0 (0)\n16 (8.6)\n24 (10.6)\nChills\n4 (12.5)\n0 (0)\n0 (0)\n14 (7.6)\n18 (7.9)\nDiarrhea\n3 (9.4)\n0 (0)\n0 (0)\n15 (8.1)\n18 (7.9)\nNausea or vomiting\n3 (9.4)\n0 (0)\n0 (0)\n14 (7.6)\n17 (7.5)\nLoss of taste\n8 (25.0)\n2 (25.0)\n1 (50.0)\n3 (1.6)\n14 (6.2)\nLoss of smell\n8 (25.0)\n2 (25.0)\n1 (50.0)\n2 (1.1)\n13 (5.7)\nFever\n6 (18.8)\n0 (0)\n0 (0)\n5 (2.7)\n11 (4.8)\nDifficulty breathing\n3 (9.4)\n0 (0)\n0 (0)\n8 (4.3)\n11 (4.8)\nAbdominal pain\n1 (3.1)\n0 (0)\n0 (0)\n6 (3.2)\n7 (3.1)\nRigors\n0 (0)\n0 (0)\n0 (0)\n0 (0)\n0 (0.0)\nOther reported symptoms***\n1 (3.1)\n0 (0)\n0 (0)\n4 (2.2)\n5 (2.2)\nSymptom onset date reported\n31 (96.9)\n8 (100.0)\n2 (100.0)\n169 (91.4)\n210 (92.5)\n≤5 days between reported symptom onset and specimen collection\n23 (74.2)\n8 (100.0)\n1 (50.0)\n120 (71.0)\n152 (72.4)\n* Includes 57 participants who received multiple tests and were included more than once in the analysis.\n†\nTrue positive = antigen-positive and real-time RT-PCR–positive; false negative = antigen-negative and real-time RT-PCR–positive; false positive = antigen-positive and real-time RT-PCR–negative; true negative = antigen-negative and real-time RT-PCR–negative; these definitions do not reflect results from viral culture.\n§\nAt university A, real-time RT-PCR was performed using the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2.\n¶\nAt university B, real-time RT-PCR was performed using Thermo Fisher Scientific’s TaqPath COVID-19 Combo Kit for detection of SARS-CoV-2.\n** One university staff member’s child aged 15 years. All other participants were aged ≥17 years.\n††\nNon-Hispanic ethnicity represented for all White, Black\/African-American, Asian\/Pacific Islander, American Indian\/Alaska Native, Other\/Unknown\/Multiple races.\n§§\nOther affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members.\n¶¶\nEver in close contact was defined as within 6 feet for ≥15 minutes of a person with a diagnosis of COVID-19.\n*** Other reported symptoms included allergies, cough that is not dry, and difficulty breathing from anxiety.\nTABLE 2. Sensitivity, specificity, positive predictive value, and negative predictive value of Sofia SARS Antigen Fluorescent Immunoassay compared with real-time reverse transcription–polymerase chain reaction (RT-PCR) among asymptomatic and symptomatic persons — two universities, Wisconsin, September–October 2020\nAntigen test result\nReal-time RT-PCR result, no.\nAsymptomatic (N = 871)\nSymptomatic* (N = 227)\nPositive\nNegative\nTotal\nPositive\nNegative\nTotal\nPositive\n7\n14\n21\n32\n2\n34\nNegative\n10\n840\n850\n8\n185\n193\nTotal\n17\n854\n871\n40\n187\n227\nTest evaluation, % (95% CI)\nSensitivity\n41.2 (18.4–67.1)\n80.0 (64.4–90.9)\nSpecificity\n98.4 (97.3–99.1)\n98.9 (96.2–99.9)\nPositive predictive value\n33.3 (14.6–57.0)\n94.1 (80.3–99.3)\nNegative predictive value\n98.8 (97.8–99.4)\n95.9 (92.0–98.2)\nAbbreviation:\nCI = confidence interval.\n* One or more symptoms reported.\nFIGURE\n.\nViral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) results (n = 69),* by cycle threshold (Ct) value† and the interval between specimen collection and reported symptom onset or asymptomatic status — university A, Wisconsin, September–October 2020\n* n = 30 antigen- and culture-positive; n = 22 antigen-positive and culture-negative; n = 15 antigen- and culture-negative; n = two antigen- negative and culture-positive.\n†\nCt values represent cycle thresholds for the N1 target probe during SARS-CoV-2 real-time RT-PCR; Ct values are represented on the y-axis in descending order to indicate that lower Ct values represent higher levels of RNA in the specimen.\nSuggested citation for this article:\nPray IW, Ford L, Cole D, et al. Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020. MMWR Morb Mortal Wkly Rep 2021;69:1642–1647. DOI:\nhttp:\/\/dx.doi.org\/10.15585\/mmwr.mm695152a3\n.\nMMWR\nand\nMorbidity and Mortality Weekly Report\nare service marks of the U.S. Department of Health and Human Services.\nUse of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of \nHealth and Human Services.\nReferences to non-CDC sites on the Internet are \nprovided as a service to\nMMWR\nreaders and do not constitute or imply \nendorsement of these organizations or their programs by CDC or the U.S. \nDepartment of Health and Human Services. CDC is not responsible for the content \nof pages found at these sites. URL addresses listed in\nMMWR\nwere current as of \nthe date of publication.\nAll HTML versions of\nMMWR\narticles are generated from final proofs through an automated process. \nThis conversion might result in character translation or format errors in the HTML version. \nUsers are referred to the electronic PDF version (\nhttps:\/\/www.cdc.gov\/mmwr\n) \nand\/or the original\nMMWR\npaper copy for printable versions of official text, figures, and tables.\nQuestions or messages regarding errors in formatting should be addressed to\nmmwrq@cdc.gov\n.","attrs_markdown":"[Skip directly to site content](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#content) [Skip directly to search](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#headerSearch)\n\n[Español](https:\/\/www.cdc.gov\/spanish\/) \\|  [Other Languages](https:\/\/wwwn.cdc.gov\/pubs\/other-languages\/)\n\n![](https:\/\/www.cdc.gov\/TemplatePackage\/4.0\/assets\/imgs\/uswds\/us_flag_small.png)\n\nAn official website of the United States government\n\nHere's how you know\n\n![](https:\/\/www.cdc.gov\/TemplatePackage\/4.0\/assets\/imgs\/uswds\/icon-dot-gov.svg)\n\n**Official websites use .gov**\n\nA .gov website belongs to an official government organization in the United States.\n\n![](https:\/\/www.cdc.gov\/TemplatePackage\/4.0\/assets\/imgs\/uswds\/icon-https.svg)\n\n**Secure .gov websites use HTTPS**\n\nA lock (  ) or https:\/\/ means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.\n\n[Centers for Disease Control and Prevention. CDC twenty four seven. Saving Lives, Protecting People ![CDC Logo](https:\/\/www.cdc.gov\/TemplatePackage\/4.0\/assets\/imgs\/logo\/logo-notext.svg) ![CDC Logo](https:\/\/www.cdc.gov\/TemplatePackage\/4.0\/assets\/imgs\/logo\/logo-notext.svg)](https:\/\/www.cdc.gov\/)   [Morbidity and Mortality Weekly Report (*MMWR*)](https:\/\/www.cdc.gov\/mmwr\/index.html)\n\n![](data:image\/jpeg;base64,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)\n\n[Morbidity and Mortality Weekly Report (*MMWR*)](https:\/\/www.cdc.gov\/mmwr\/index.html)\n\n[Morbidity and Mortality Weekly Report (*MMWR*)](https:\/\/www.cdc.gov\/mmwr\/index.html)\n\n# Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020\n*Weekly* \/ January 1, 2021 \/ 69(5152);1642–1647\n\n[Print](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#print)\n\nRelated Pages\n\n***Please note:** This report has been corrected.*\n\nIan W. Pray, PhD1,2,3,\\*; Laura Ford, PhD1,2,\\*; Devlin Cole, MD3,4; Christine Lee, PhD1,5; John Paul Bigouette, PhD1,2; Glen R. Abedi, MPH1; Dena Bushman, MSN, MPH1,2; Miranda J. Delahoy, PhD1,2; Dustin Currie, PhD1,2; Blake Cherney, MS1; Marie Kirby, PhD1; Geroncio Fajardo, MD1; Motria Caudill, PhD1,6; Kimberly Langolf, MS7; Juliana Kahrs, MS7; Patrick Kelly, MD4,8; Collin Pitts, MD4,8; Ailam Lim, PhD9; Nicole Aulik, PhD9; Azaibi Tamin, PhD1; Jennifer L. Harcourt, PhD1; Krista Queen, PhD1; Jing Zhang, PhD1; Brett Whitaker, PhD1; Hannah Browne1; Magdalena Medrzycki, PhD1; Patricia Shewmaker, PhD1; Jennifer Folster, PhD1; Bettina Bankamp, PhD1; Michael D. Bowen, PhD1; Natalie J. Thornburg, PhD1; Kimberly Goffard, MBA10; Brandi Limbago, PhD1; Allen Bateman, PhD7,11; Jacqueline E. Tate, PhD1; Douglas Gieryn10; Hannah L. Kirking, MD1; Ryan Westergaard, MD, PhD3,4; Marie Killerby, VetMB1; CDC COVID-19 Surge Laboratory Group ([View author affiliations](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#contribAff))\n\n[View suggested citation](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#suggestedcitation)\n\n### **Summary**\n**What is already known about this topic?**\n\nAntigen tests for SARS-CoV-2 are inexpensive and can return results within 15 minutes, but test performance data in asymptomatic and symptomatic persons are limited.\n\n**What is added by this report?**\n\nCompared with real-time reverse transcription–polymerase chain reaction (RT-PCR) testing, the Sofia antigen test had a sensitivity of 80.0% and specificity of 98.9% among symptomatic persons; accuracy was lower (sensitivity 41.2% and specificity 98.4%) when used for screening of asymptomatic persons.\n\n**What are the implications for public health practice?**\n\nTo account for reduced antigen test accuracy, confirmatory testing with a nucleic acid amplification test (e.g., RT-PCR) should be considered after negative antigen test results in symptomatic persons and positive antigen test results in asymptomatic persons.\n\nArticle Metrics\n\n##### Altmetric:\n[![Article has an altmetric score of 2033](https:\/\/badges.altmetric.com\/?size=128&score=2033&types=mbvcrtfd)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238)\n\n[See more details](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238)\n\n[News (43)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=news)\n\n[Blogs (7)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=blogs)\n\n[Policy documents (3)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=policy-documents)\n\n[X (2647)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=twitter)\n\n[Facebook (9)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=facebook)\n\n[Reddit (59)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=reddit)\n\n[Video (1)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=video)\n\n[Clinical guidelines (2)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=guidelines)\n\n[Podcasts (1)](https:\/\/www.altmetric.com\/details.php?domain=www.cdc.gov&citation_id=96939238&tab=podcasts)\n\nMendeley (295)\n\n[**Figure**](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#F1_down)\n\n**Tables**\n\n[Table 1](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#T1_down)\n\n[Table 2](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#T2_down)\n\nRelated Materials\n\n- [PDF \\[142K\\]](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/pdfs\/mm695152a3-H.pdf)\n\n[![The figure is a visual abstract describing that COVID-19 rapid tests are inexpensive and fast but sometimes give incorrect results.](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/social-media\/mm695152a3_RapidAntigenTestResultsCOVID19_IMAGE_01Jan21_1200x675.jpg?_=41053)\\[JPG - 135 KB\\]](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/social-media\/mm695152a3_RapidAntigenTestResultsCOVID19_IMAGE_01Jan21_1200x675.jpg)\n\n## Discussion\nThe Sofia SARS Antigen FIA received FDA EUA on May 8, 2020, for use in symptomatic persons within 5 days of symptom onset (*2*). In this investigation, among persons reporting COVID-19–compatible symptoms at specimen collection, the test was less accurate (sensitivity = 80.0%; specificity = 98.9%) than reported in the FDA EUA (sensitivity = 96.7%; specificity = 100%) (*2*). Two of eight specimens from symptomatic persons that had false-negative antigen test results were positive by viral culture, indicating that potentially infectious persons might not be detected by antigen testing. To reduce the impact of false-negative antigen test results, confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, should be considered following negative antigen test results in symptomatic persons (*1*).\n\nAmong asymptomatic participants, antigen test sensitivity was 41.2%, specificity was 98.4%, and PPV in this population was 33.3%. This low PPV was observed despite a relatively high prevalence of SARS-CoV-2 in this population (5.2% prevalence overall; 2.0% among asymptomatic persons), suggesting that PPV could be even lower when using this antigen test among populations with lower expected SARS-CoV-2 prevalence. To account for false-positive results when using antigen tests for asymptomatic screening, confirmatory NAAT testing should be considered following positive antigen test results in asymptomatic persons, particularly when pretest probability of SARS-CoV-2 infection is low (*1*). The NPV of antigen testing among asymptomatic participants was 98.8%, and virus was not cultured from asymptomatic participants with antigen-negative results, indicating that asymptomatic persons with negative antigen results are unlikely to be infected with SARS-CoV-2 and would not require confirmatory NAAT (*1*).\n\nThe findings in this report are subject to at least four limitations. First, participants were predominantly young adults in university settings where ongoing serial testing was being conducted. Antigen test performance might differ in other populations with different characteristics and testing schedules. Second, given the limitations of RT-PCR, some false-positive antigen test results might represent true infections not identified by RT-PCR. Third, the ability to recover infectious virus in culture is limited and decreases for specimens with higher Ct values (*8*); a lack of virus recovery by culture does not indicate that a person is not infectious. Finally, this investigation evaluated the Sofia SARS Antigen FIA, and cannot be generalized to other FDA-authorized SARS-CoV-2 antigen tests.\n\nSerial testing of asymptomatic and symptomatic persons has been proposed for prevention and control of SARS-CoV-2 transmission (*9*,*10*) and is currently being implemented at U.S. colleges and universities and in other congregate settings (*3*–*5*). Despite reduced sensitivity compared with real-time RT-PCR, the use of antigen tests for serial testing in these settings, particularly when RT-PCR tests are not available or have a prolonged turnaround time, might still allow rapid identification of infectious persons and control of outbreaks (*1*). However, antigen-based testing strategies should account for the lower sensitivity and lower PPV when used for asymptomatic screening by considering confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, after a positive antigen test result in an asymptomatic person. Confirmatory testing should also be considered following a negative antigen test result in a person experiencing COVID-19–compatible symptoms. All persons with negative antigen test results should continue to take measures to prevent SARS-CoV-2 transmission, including wearing a mask, reducing contact with nonhousehold members, and getting tested if they experience symptoms or have close contact with someone who has COVID-19.††† Symptomatic persons with negative antigen test results should continue to follow CDC guidance§§§ for persons who might have COVID-19, including staying home except to get medical care and protecting household members by staying in a separate room, wearing a mask indoors, washing hands often, and frequently disinfecting surfaces.\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\n### Acknowledgments\nEdward Samuel Rivera, Daniel J. O’Donnell, University of Wisconsin-Oshkosh; Margaret Okomo-Adhiambo, Umesh Parashar, Paul Rota, Lauren Franco, Gerardo Garcia-Lerma, CDC; Neeti Dahal, Wisconsin Veterinary Diagnostic Laboratory-Wisconsin State Laboratory of Hygiene COVID Laboratory, University of Wisconsin-Madison.\n\n### CDC COVID-19 Surge Laboratory Group\nBaoming Jiang, CDC; Jan Vinjé, CDC; Amy L. Hopkins, CDC; Eric Katz, CDC; Leslie Barclay, CDC; Mathew Esona, CDC; Rashi Gautam, CDC; Slavica Mijatovic-Rustempasic, CDC; Sung-Sil Moon, CDC; Theresa Bessey, CDC; Preeti Chhabra, CDC; Sarah L. Smart, CDC; Raydel Anderson, CDC; Kay W. Radford, CDC; Gimin Kim, CDC; Dexter Thompson, CDC; Congrong Miao, CDC; Min-hsin Chen, CDC; Lalitha Gade, CDC; Renee Galloway, CDC; Kashif Sahibzada, CDC; Nhien M. Tran, CDC; Srinivasan Velusamy, CDC; HaoQiang Zheng, CDC; Kenny Nguyen, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Claire Hartloge, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Brent Jenkins, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Phili Wong, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\nCorresponding author: Ian Pray, [ian.pray@dhs.wisconsin.gov](mailto:ian.pray@dhs.wisconsin.gov).\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n***\n1CDC COVID-19 Response Team; 2Epidemic Intelligence Service, CDC; 3Wisconsin Department of Health Services; 4School of Medicine and Public Health, University of Wisconsin-Madison; 5Laboratory Leadership Service, CDC; 6Agency for Toxic Substances and Disease Registry, Atlanta, Georgia; 7University of Wisconsin-Oshkosh; 8University Health Services, University of Wisconsin-Madison; 9Wisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison; 10Winnebago County Health Department, Oshkosh, Wisconsin; 11Wisconsin State Laboratory of Hygiene.\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\nAll authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\n\\* These authors contributed equally to this report.\n\n† Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members.\n\n§ Symptom list was based on the interim position statement for COVID-19 case definitions from the Council of State and Territorial Epidemiologists, updated August 7, 2020. Clinical criteria for COVID-19 included fever, cough, shortness of breath, fatigue, sore throat, headache, muscle aches, chills, nasal congestion, difficulty breathing, diarrhea, nausea, vomiting, abdominal pain, rigors, loss of taste, and loss of smell. <https:\/\/cdn.ymaws.com\/www.cste.org\/resource\/resmgr\/ps\/positionstatement2020\/Interim-20-ID-02_COVID-19.pdf>.\n\n¶ Recent exposure was defined as being within 6 feet of a person with a COVID-19 diagnosis for ≥15 minutes in the past 14 days.\n\n\\*\\* <https:\/\/www.fda.gov\/media\/137885\/download>.\n\n†† Specimens were used to perform a limiting-dilution inoculation of Vero CCL-81 cells, and cultures showing evidence of cytopathic effect (CPE) were tested by real-time RT-PCR for the presence of SARS-CoV-2 RNA. Viral recovery was defined as any culture in which the first passage had an N1 Ct at least twofold lower than the corresponding clinical specimen.\n\n§§ Ct values from real-time RT-PCR were only compared for specimens collected at university A that were analyzed with the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2.\n\n¶¶ 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq.\n\n\\*\\*\\* The participant with a false-negative result 2 days after symptom onset had a repeat specimen 2 days later; the results of testing were positive by antigen test and by real-time RT-PCR.\n\n††† <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/prevent-getting-sick\/prevention.html>.\n\n§§§ <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/if-you-are-sick\/steps-when-sick.html>.\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\n## References\n1. CDC. Coronavirus disease 2019 (COVID-19): interim guidance for antigen testing for SARS-CoV-2. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/lab\/resources\/antigen-tests-guidelines.html>\n2. Food and Drug Administration. In vitro diagnostics EUAs. Silver Spring, MD: US Department of Health and Human Services, Food and Drug Administration; 2020. <https:\/\/www.fda.gov\/medical-devices\/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices\/vitro-diagnostics-euas>\n3. CDC. Coronavirus disease 2019 (COVID-19): guidance for testing, screening, and outbreak response for institutions of higher education (IHEs). Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/community\/colleges-universities\/ihe-testing.html>\n4. CDC. Coronavirus disease 2019 (COVID-19): testing guidelines for nursing homes. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/hcp\/nursing-homes-testing.html>\n5. CDC. Coronavirus disease 2019 (COVID-19): interim considerations for SARS-CoV-2 testing in correctional and detention facilities. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/community\/correction-detention\/testing.html>\n6. Lu X, Wang L, Sakthivel SK, et al. US CDC real-time reverse transcription PCR panel for detection of severe acute respiratory syndrome coronavirus 2. Emerg Infect Dis 2020;26:1654–65. [CrossRef](http:\/\/dx.doi.org\/10.3201\/eid2608.201246) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32396505)\n7. Harcourt J, Tamin A, Lu X, et al. Severe acute respiratory syndrome coronavirus 2 from patient with coronavirus disease, United States. Emerg Infect Dis 2020;26:1266–73. [CrossRef](http:\/\/dx.doi.org\/10.3201\/eid2606.200516) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32160149)\n8. Gniazdowski V, Morris CP, Wohl S, et al. Repeat COVID-19 molecular testing: correlation of SARS-CoV-2 culture with molecular assays and cycle thresholds. Clin Infect Dis 2020;ciaa1616. [CrossRef](http:\/\/dx.doi.org\/10.1093\/cid\/ciaa1616) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/33104776)\n9. Walke HT, Honein MA, Redfield RR. Preventing and responding to COVID-19 on college campuses. JAMA 2020;324:1727–8. [CrossRef](http:\/\/dx.doi.org\/10.1001\/jama.2020.20027) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32991681)\n10. Paltiel AD, Zheng A, Walensky RP. Assessment of SARS-CoV-2 screening strategies to permit the safe reopening of college campuses in the United States. JAMA Netw Open 2020;3:e2016818. [CrossRef](http:\/\/dx.doi.org\/10.1001\/jamanetworkopen.2020.16818) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32735339)\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\n| Characteristic | No (%) |   |   |   |   |\n|---|---|---|---|---|---|\n| True positives (N = 39) | False negatives (N = 18) | False positives (N = 16) | True negatives (N = 1,025) | Total (N = 1,098) |   |\n| ****Testing site**** |   |   |   |   |   |\n| University A§ | 37 (94.9) | 17 (94.4) | 15 (93.8) | 982 (95.8) | ****1,051 (95.7)**** |\n| University B¶ | 2 (5.1) | 1 (5.6) | 1 (6.3) | 43 (4.2) | ****47 (4.3)**** |\n| ****Sex**** |   |   |   |   |   |\n| Male | 16 (41.0) | 9 (50.0) | 12 (75.0) | 416 (40.6) | ****453 (41.3)**** |\n| Female | 23 (59.0) | 9 (50.0) | 4 (25.0) | 609 (59.4) | ****645 (58.7)**** |\n| ****Age group (yrs)**** |   |   |   |   |   |\n| 15–24\\*\\* | 35 (89.7) | 16 (88.9) | 11 (68.8) | 909 (88.7) | ****971 (88.4)**** |\n| ≥25 | 4 (10.3) | 2 (11.1) | 5 (31.3) | 116 (11.3) | ****127 (11.6)**** |\n| ****Race\/Ethnicity††**** |   |   |   |   |   |\n| White | 31 (79.5) | 17 (94.4) | 12 (75.0) | 857 (83.6) | ****917 (83.5)**** |\n| Hispanic\/Latino | 6 (15.4) | 0 (0) | 1 (6.3) | 54 (5.3) | ****61 (5.6)**** |\n| Black\/African-American | 0 (0) | 1 (5.6) | 2 (12.5) | 26 (2.5) | ****29 (2.6)**** |\n| Asian\/Pacific Islander | 0 (0) | 0 (0) | 0 (0) | 49 (4.8) | ****49 (4.5)**** |\n| American Indian\/Alaska Native | 0 (0) | 0 (0) | 0 (0) | 3 (0.3) | ****3 (0.3)**** |\n| Other\/Unknown\/Multiple races | 2 (5.1) | 0 (0) | 1 (6.3) | 36 (3.5) | ****39 (3.6)**** |\n| ****University status**** |   |   |   |   |   |\n| Student | 35 (89.7) | 17 (94.4) | 13 (81.3) | 929 (90.6) | ****994 (90.5)**** |\n| Faculty or staff member | 4 (10.3) | 1 (5.6) | 3 (18.8) | 74 (7.2) | ****82 (7.5)**** |\n| Other affiliate or unknown§§ | 0 (0) | 0 (0) | 0 (0) | 22 (2.2) | ****22 (2.0)**** |\n| ****Exposure****¶¶ ****to a COVID-19 case**** |   |   |   |   |   |\n| Been in close contact in the past 14 days | 13 (33.3) | 9 (50.0) | 4 (25.0) | 128 (12.5) | ****154 (14.0)**** |\n| ****Quarantine status**** |   |   |   |   |   |\n| Quarantined at time of specimen collection | 17 (43.6) | 6 (33.3) | 3 (18.8) | 109 (10.6) | ****135 (12.3)**** |\n| Time between quarantine initiation to specimen collection, median days (range) | 1 (0–8) | 3\\.5 (0–6) | 1 (0–4) | 4 (0–28) | ****4 (0–28)**** |\n| ****Reported symptoms**** |   |   |   |   |   |\n| No current symptoms | 7 (17.9) | 10 (55.6) | 14 (87.5) | 840 (82.0) | ****871 (79.3)**** |\n| One or more symptoms in the past 14 days | 2 (28.6) | 1 (10.0) | 0 (0) | 50 (6.0) | ****53 (6.1)**** |\n| No symptoms in the past 14 days | 5 (71.4) | 9 (90.0) | 14 (100.0) | 790 (94.0) | ****818 (93.9)**** |\n| One or more current symptoms | 32 (82.1) | 8 (44.4) | 2 (12.5) | 185 (18.0) | 227 (20.7) |\n| Nasal congestion | 24 (75.0) | 2 (25.0) | 1 (50.0) | 87 (47.0) | ****114 (50.2)**** |\n| Sore throat | 12 (37.5) | 5 (62.5) | 1 (50.0) | 79 (42.7) | ****97 (42.7)**** |\n| Headache | 17 (53.1) | 3 (37.5) | 1 (50.0) | 66 (35.7) | ****87 (38.3)**** |\n| Cough | 18 (56.3) | 6 (75.0) | 1 (50.0) | 45 (24.3) | ****70 (30.8)**** |\n| Fatigue | 14 (43.8) | 3 (37.5) | 1 (50.0) | 42 (22.7) | ****60 (26.4)**** |\n| Muscle aches | 11 (34.4) | 2 (25.0) | 0 (0) | 30 (16.2) | ****43 (18.9)**** |\n| Shortness of breath | 7 (21.9) | 1 (12.5) | 0 (0) | 16 (8.6) | ****24 (10.6)**** |\n| Chills | 4 (12.5) | 0 (0) | 0 (0) | 14 (7.6) | ****18 (7.9)**** |\n| Diarrhea | 3 (9.4) | 0 (0) | 0 (0) | 15 (8.1) | ****18 (7.9)**** |\n| Nausea or vomiting | 3 (9.4) | 0 (0) | 0 (0) | 14 (7.6) | ****17 (7.5)**** |\n| Loss of taste | 8 (25.0) | 2 (25.0) | 1 (50.0) | 3 (1.6) | ****14 (6.2)**** |\n| Loss of smell | 8 (25.0) | 2 (25.0) | 1 (50.0) | 2 (1.1) | ****13 (5.7)**** |\n| Fever | 6 (18.8) | 0 (0) | 0 (0) | 5 (2.7) | ****11 (4.8)**** |\n| Difficulty breathing | 3 (9.4) | 0 (0) | 0 (0) | 8 (4.3) | ****11 (4.8)**** |\n| Abdominal pain | 1 (3.1) | 0 (0) | 0 (0) | 6 (3.2) | ****7 (3.1)**** |\n| Rigors | 0 (0) | 0 (0) | 0 (0) | 0 (0) | ****0 (0.0)**** |\n| Other reported symptoms\\*\\*\\* | 1 (3.1) | 0 (0) | 0 (0) | 4 (2.2) | ****5 (2.2)**** |\n| ****Symptom onset date reported**** | 31 (96.9) | 8 (100.0) | 2 (100.0) | 169 (91.4) | ****210 (92.5)**** |\n| ≤5 days between reported symptom onset and specimen collection | 23 (74.2) | 8 (100.0) | 1 (50.0) | 120 (71.0) | ****152 (72.4)**** |\n\n\\* Includes 57 participants who received multiple tests and were included more than once in the analysis.  \n † True positive = antigen-positive and real-time RT-PCR–positive; false negative = antigen-negative and real-time RT-PCR–positive; false positive = antigen-positive and real-time RT-PCR–negative; true negative = antigen-negative and real-time RT-PCR–negative; these definitions do not reflect results from viral culture.  \n § At university A, real-time RT-PCR was performed using the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2.  \n ¶ At university B, real-time RT-PCR was performed using Thermo Fisher Scientific’s TaqPath COVID-19 Combo Kit for detection of SARS-CoV-2.  \n \\*\\* One university staff member’s child aged 15 years. All other participants were aged ≥17 years.  \n †† Non-Hispanic ethnicity represented for all White, Black\/African-American, Asian\/Pacific Islander, American Indian\/Alaska Native, Other\/Unknown\/Multiple races.  \n §§ Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members.  \n ¶¶ Ever in close contact was defined as within 6 feet for ≥15 minutes of a person with a diagnosis of COVID-19.  \n \\*\\*\\* Other reported symptoms included allergies, cough that is not dry, and difficulty breathing from anxiety.\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\n| Antigen test result | Real-time RT-PCR result, no. |   |   |   |   |   |\n|---|---|---|---|---|---|---|\n| Asymptomatic (N = 871) | Symptomatic\\* (N = 227) |   |   |   |   |   |\n| Positive | Negative | Total | Positive | Negative | Total |   |\n| Positive | 7 | 14 | ****21**** | 32 | 2 | ****34**** |\n| Negative | 10 | 840 | ****850**** | 8 | 185 | ****193**** |\n| ****Total**** | ****17**** | ****854**** | ****871**** | ****40**** | ****187**** | ****227**** |\n| ****Test evaluation, % (95% CI)**** |   |   |   |   |   |   |\n| Sensitivity | 41\\.2 (18.4–67.1) | 80\\.0 (64.4–90.9) |   |   |   |   |\n| Specificity | 98\\.4 (97.3–99.1) | 98\\.9 (96.2–99.9) |   |   |   |   |\n| Positive predictive value | 33\\.3 (14.6–57.0) | 94\\.1 (80.3–99.3) |   |   |   |   |\n| Negative predictive value | 98\\.8 (97.8–99.4) | 95\\.9 (92.0–98.2) |   |   |   |   |\n\n****Abbreviation:**** CI = confidence interval.  \n \\* One or more symptoms reported.\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\n##### [![Return to your place in the text](https:\/\/www.cdc.gov\/images\/arrow_up.gif)](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#F1_up)**FIGURE**. **Viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) results (n = 69),\\* by cycle threshold (Ct) value† and the interval between specimen collection and reported symptom onset or asymptomatic status — university A, Wisconsin, September–October 2020**\n![The figure is a scatterplot showing viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction results (n = 69), by cycle threshold value and the interval between specimen collection and reported symptom onset or asymptomatic status at university A in Wisconsin during September–October 2020.](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/figures\/mm695152a3-F.gif?_=47024)\n\n\\* n = 30 antigen- and culture-positive; n = 22 antigen-positive and culture-negative; n = 15 antigen- and culture-negative; n = two antigen- negative and culture-positive.\n\n† Ct values represent cycle thresholds for the N1 target probe during SARS-CoV-2 real-time RT-PCR; Ct values are represented on the y-axis in descending order to indicate that lower Ct values represent higher levels of RNA in the specimen.\n\n[Top](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm)\n\n**Suggested citation for this article:** Pray IW, Ford L, Cole D, et al. Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020. MMWR Morb Mortal Wkly Rep 2021;69:1642–1647. DOI: <http:\/\/dx.doi.org\/10.15585\/mmwr.mm695152a3>.\n\n*MMWR* and *Morbidity and Mortality Weekly Report* are service marks of the U.S. Department of Health and Human Services.  \n Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services.   \nReferences to non-CDC sites on the Internet are provided as a service to *MMWR* readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. 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Pray, PhD1,2,3,\\*; Laura Ford, PhD1,2,\\*; Devlin Cole, MD3,4; Christine Lee, PhD1,5; John Paul Bigouette, PhD1,2; Glen R. Abedi, MPH1; Dena Bushman, MSN, MPH1,2; Miranda J. Delahoy, PhD1,2; Dustin Currie, PhD1,2; Blake Cherney, MS1; Marie Kirby, PhD1; Geroncio Fajardo, MD1; Motria Caudill, PhD1,6; Kimberly Langolf, MS7; Juliana Kahrs, MS7; Patrick Kelly, MD4,8; Collin Pitts, MD4,8; Ailam Lim, PhD9; Nicole Aulik, PhD9; Azaibi Tamin, PhD1; Jennifer L. Harcourt, PhD1; Krista Queen, PhD1; Jing Zhang, PhD1; Brett Whitaker, PhD1; Hannah Browne1; Magdalena Medrzycki, PhD1; Patricia Shewmaker, PhD1; Jennifer Folster, PhD1; Bettina Bankamp, PhD1; Michael D. Bowen, PhD1; Natalie J. Thornburg, PhD1; Kimberly Goffard, MBA10; Brandi Limbago, PhD1; Allen Bateman, PhD7,11; Jacqueline E. Tate, PhD1; Douglas Gieryn10; Hannah L. Kirking, MD1; Ryan Westergaard, MD, PhD3,4; Marie Killerby, VetMB1; CDC COVID-19 Surge Laboratory Group ([View author affiliations](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#contribAff))\n\n[View suggested citation](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#suggestedcitation)\n\n### **Summary**\n**What is already known about this topic?**\n\nAntigen tests for SARS-CoV-2 are inexpensive and can return results within 15 minutes, but test performance data in asymptomatic and symptomatic persons are limited.\n\n**What is added by this report?**\n\nCompared with real-time reverse transcription–polymerase chain reaction (RT-PCR) testing, the Sofia antigen test had a sensitivity of 80.0% and specificity of 98.9% among symptomatic persons; accuracy was lower (sensitivity 41.2% and specificity 98.4%) when used for screening of asymptomatic persons.\n\n**What are the implications for public health practice?**\n\nTo account for reduced antigen test accuracy, confirmatory testing with a nucleic acid amplification test (e.g., RT-PCR) should be considered after negative antigen test results in symptomatic persons and positive antigen test results in asymptomatic persons.\n\n##### Altmetric:\nMendeley (295)\n\n## Discussion\nThe Sofia SARS Antigen FIA received FDA EUA on May 8, 2020, for use in symptomatic persons within 5 days of symptom onset (*2*). In this investigation, among persons reporting COVID-19–compatible symptoms at specimen collection, the test was less accurate (sensitivity = 80.0%; specificity = 98.9%) than reported in the FDA EUA (sensitivity = 96.7%; specificity = 100%) (*2*). Two of eight specimens from symptomatic persons that had false-negative antigen test results were positive by viral culture, indicating that potentially infectious persons might not be detected by antigen testing. To reduce the impact of false-negative antigen test results, confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, should be considered following negative antigen test results in symptomatic persons (*1*).\n\nAmong asymptomatic participants, antigen test sensitivity was 41.2%, specificity was 98.4%, and PPV in this population was 33.3%. This low PPV was observed despite a relatively high prevalence of SARS-CoV-2 in this population (5.2% prevalence overall; 2.0% among asymptomatic persons), suggesting that PPV could be even lower when using this antigen test among populations with lower expected SARS-CoV-2 prevalence. To account for false-positive results when using antigen tests for asymptomatic screening, confirmatory NAAT testing should be considered following positive antigen test results in asymptomatic persons, particularly when pretest probability of SARS-CoV-2 infection is low (*1*). The NPV of antigen testing among asymptomatic participants was 98.8%, and virus was not cultured from asymptomatic participants with antigen-negative results, indicating that asymptomatic persons with negative antigen results are unlikely to be infected with SARS-CoV-2 and would not require confirmatory NAAT (*1*).\n\nThe findings in this report are subject to at least four limitations. First, participants were predominantly young adults in university settings where ongoing serial testing was being conducted. Antigen test performance might differ in other populations with different characteristics and testing schedules. Second, given the limitations of RT-PCR, some false-positive antigen test results might represent true infections not identified by RT-PCR. Third, the ability to recover infectious virus in culture is limited and decreases for specimens with higher Ct values (*8*); a lack of virus recovery by culture does not indicate that a person is not infectious. Finally, this investigation evaluated the Sofia SARS Antigen FIA, and cannot be generalized to other FDA-authorized SARS-CoV-2 antigen tests.\n\nSerial testing of asymptomatic and symptomatic persons has been proposed for prevention and control of SARS-CoV-2 transmission (*9*,*10*) and is currently being implemented at U.S. colleges and universities and in other congregate settings (*3*–*5*). Despite reduced sensitivity compared with real-time RT-PCR, the use of antigen tests for serial testing in these settings, particularly when RT-PCR tests are not available or have a prolonged turnaround time, might still allow rapid identification of infectious persons and control of outbreaks (*1*). However, antigen-based testing strategies should account for the lower sensitivity and lower PPV when used for asymptomatic screening by considering confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, after a positive antigen test result in an asymptomatic person. Confirmatory testing should also be considered following a negative antigen test result in a person experiencing COVID-19–compatible symptoms. All persons with negative antigen test results should continue to take measures to prevent SARS-CoV-2 transmission, including wearing a mask, reducing contact with nonhousehold members, and getting tested if they experience symptoms or have close contact with someone who has COVID-19.††† Symptomatic persons with negative antigen test results should continue to follow CDC guidance§§§ for persons who might have COVID-19, including staying home except to get medical care and protecting household members by staying in a separate room, wearing a mask indoors, washing hands often, and frequently disinfecting surfaces.\n\n### Acknowledgments\nEdward Samuel Rivera, Daniel J. O’Donnell, University of Wisconsin-Oshkosh; Margaret Okomo-Adhiambo, Umesh Parashar, Paul Rota, Lauren Franco, Gerardo Garcia-Lerma, CDC; Neeti Dahal, Wisconsin Veterinary Diagnostic Laboratory-Wisconsin State Laboratory of Hygiene COVID Laboratory, University of Wisconsin-Madison.\n\n### CDC COVID-19 Surge Laboratory Group\nBaoming Jiang, CDC; Jan Vinjé, CDC; Amy L. Hopkins, CDC; Eric Katz, CDC; Leslie Barclay, CDC; Mathew Esona, CDC; Rashi Gautam, CDC; Slavica Mijatovic-Rustempasic, CDC; Sung-Sil Moon, CDC; Theresa Bessey, CDC; Preeti Chhabra, CDC; Sarah L. Smart, CDC; Raydel Anderson, CDC; Kay W. Radford, CDC; Gimin Kim, CDC; Dexter Thompson, CDC; Congrong Miao, CDC; Min-hsin Chen, CDC; Lalitha Gade, CDC; Renee Galloway, CDC; Kashif Sahibzada, CDC; Nhien M. Tran, CDC; Srinivasan Velusamy, CDC; HaoQiang Zheng, CDC; Kenny Nguyen, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Claire Hartloge, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Brent Jenkins, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Phili Wong, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee\n***\n1CDC COVID-19 Response Team; 2Epidemic Intelligence Service, CDC; 3Wisconsin Department of Health Services; 4School of Medicine and Public Health, University of Wisconsin-Madison; 5Laboratory Leadership Service, CDC; 6Agency for Toxic Substances and Disease Registry, Atlanta, Georgia; 7University of Wisconsin-Oshkosh; 8University Health Services, University of Wisconsin-Madison; 9Wisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison; 10Winnebago County Health Department, Oshkosh, Wisconsin; 11Wisconsin State Laboratory of Hygiene.\n\nAll authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.\n\n\\* These authors contributed equally to this report.\n\n† Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members.\n\n§ Symptom list was based on the interim position statement for COVID-19 case definitions from the Council of State and Territorial Epidemiologists, updated August 7, 2020. Clinical criteria for COVID-19 included fever, cough, shortness of breath, fatigue, sore throat, headache, muscle aches, chills, nasal congestion, difficulty breathing, diarrhea, nausea, vomiting, abdominal pain, rigors, loss of taste, and loss of smell. <https:\/\/cdn.ymaws.com\/www.cste.org\/resource\/resmgr\/ps\/positionstatement2020\/Interim-20-ID-02_COVID-19.pdf>.\n\n¶ Recent exposure was defined as being within 6 feet of a person with a COVID-19 diagnosis for ≥15 minutes in the past 14 days.\n\n\\*\\* <https:\/\/www.fda.gov\/media\/137885\/download>.\n\n†† Specimens were used to perform a limiting-dilution inoculation of Vero CCL-81 cells, and cultures showing evidence of cytopathic effect (CPE) were tested by real-time RT-PCR for the presence of SARS-CoV-2 RNA. Viral recovery was defined as any culture in which the first passage had an N1 Ct at least twofold lower than the corresponding clinical specimen.\n\n§§ Ct values from real-time RT-PCR were only compared for specimens collected at university A that were analyzed with the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2.\n\n¶¶ 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq.\n\n\\*\\*\\* The participant with a false-negative result 2 days after symptom onset had a repeat specimen 2 days later; the results of testing were positive by antigen test and by real-time RT-PCR.\n\n††† <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/prevent-getting-sick\/prevention.html>.\n\n§§§ <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/if-you-are-sick\/steps-when-sick.html>.\n\n## References\n1. CDC. Coronavirus disease 2019 (COVID-19): interim guidance for antigen testing for SARS-CoV-2. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/lab\/resources\/antigen-tests-guidelines.html>\n2. Food and Drug Administration. In vitro diagnostics EUAs. Silver Spring, MD: US Department of Health and Human Services, Food and Drug Administration; 2020. <https:\/\/www.fda.gov\/medical-devices\/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices\/vitro-diagnostics-euas>\n3. CDC. Coronavirus disease 2019 (COVID-19): guidance for testing, screening, and outbreak response for institutions of higher education (IHEs). Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/community\/colleges-universities\/ihe-testing.html>\n4. CDC. Coronavirus disease 2019 (COVID-19): testing guidelines for nursing homes. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/hcp\/nursing-homes-testing.html>\n5. CDC. Coronavirus disease 2019 (COVID-19): interim considerations for SARS-CoV-2 testing in correctional and detention facilities. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/community\/correction-detention\/testing.html>\n6. Lu X, Wang L, Sakthivel SK, et al. US CDC real-time reverse transcription PCR panel for detection of severe acute respiratory syndrome coronavirus 2. Emerg Infect Dis 2020;26:1654–65. [CrossRef](http:\/\/dx.doi.org\/10.3201\/eid2608.201246) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32396505)\n7. Harcourt J, Tamin A, Lu X, et al. Severe acute respiratory syndrome coronavirus 2 from patient with coronavirus disease, United States. Emerg Infect Dis 2020;26:1266–73. [CrossRef](http:\/\/dx.doi.org\/10.3201\/eid2606.200516) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32160149)\n8. Gniazdowski V, Morris CP, Wohl S, et al. Repeat COVID-19 molecular testing: correlation of SARS-CoV-2 culture with molecular assays and cycle thresholds. Clin Infect Dis 2020;ciaa1616. [CrossRef](http:\/\/dx.doi.org\/10.1093\/cid\/ciaa1616) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/33104776)\n9. Walke HT, Honein MA, Redfield RR. Preventing and responding to COVID-19 on college campuses. JAMA 2020;324:1727–8. [CrossRef](http:\/\/dx.doi.org\/10.1001\/jama.2020.20027) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32991681)\n10. Paltiel AD, Zheng A, Walensky RP. Assessment of SARS-CoV-2 screening strategies to permit the safe reopening of college campuses in the United States. JAMA Netw Open 2020;3:e2016818. [CrossRef](http:\/\/dx.doi.org\/10.1001\/jamanetworkopen.2020.16818) [PubMed](http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/32735339)\n\n| Characteristic | No (%) |   |   |   |   |\n|---|---|---|---|---|---|\n| True positives (N = 39) | False negatives (N = 18) | False positives (N = 16) | True negatives (N = 1,025) | Total (N = 1,098) |   |\n| ****Testing site**** |   |   |   |   |   |\n| University A§ | 37 (94.9) | 17 (94.4) | 15 (93.8) | 982 (95.8) | ****1,051 (95.7)**** |\n| University B¶ | 2 (5.1) | 1 (5.6) | 1 (6.3) | 43 (4.2) | ****47 (4.3)**** |\n| ****Sex**** |   |   |   |   |   |\n| Male | 16 (41.0) | 9 (50.0) | 12 (75.0) | 416 (40.6) | ****453 (41.3)**** |\n| Female | 23 (59.0) | 9 (50.0) | 4 (25.0) | 609 (59.4) | ****645 (58.7)**** |\n| ****Age group (yrs)**** |   |   |   |   |   |\n| 15–24\\*\\* | 35 (89.7) | 16 (88.9) | 11 (68.8) | 909 (88.7) | ****971 (88.4)**** |\n| ≥25 | 4 (10.3) | 2 (11.1) | 5 (31.3) | 116 (11.3) | ****127 (11.6)**** |\n| ****Race\/Ethnicity††**** |   |   |   |   |   |\n| White | 31 (79.5) | 17 (94.4) | 12 (75.0) | 857 (83.6) | ****917 (83.5)**** |\n| Hispanic\/Latino | 6 (15.4) | 0 (0) | 1 (6.3) | 54 (5.3) | ****61 (5.6)**** |\n| Black\/African-American | 0 (0) | 1 (5.6) | 2 (12.5) | 26 (2.5) | ****29 (2.6)**** |\n| Asian\/Pacific Islander | 0 (0) | 0 (0) | 0 (0) | 49 (4.8) | ****49 (4.5)**** |\n| American Indian\/Alaska Native | 0 (0) | 0 (0) | 0 (0) | 3 (0.3) | ****3 (0.3)**** |\n| Other\/Unknown\/Multiple races | 2 (5.1) | 0 (0) | 1 (6.3) | 36 (3.5) | ****39 (3.6)**** |\n| ****University status**** |   |   |   |   |   |\n| Student | 35 (89.7) | 17 (94.4) | 13 (81.3) | 929 (90.6) | ****994 (90.5)**** |\n| Faculty or staff member | 4 (10.3) | 1 (5.6) | 3 (18.8) | 74 (7.2) | ****82 (7.5)**** |\n| Other affiliate or unknown§§ | 0 (0) | 0 (0) | 0 (0) | 22 (2.2) | ****22 (2.0)**** |\n| ****Exposure****¶¶ ****to a COVID-19 case**** |   |   |   |   |   |\n| Been in close contact in the past 14 days | 13 (33.3) | 9 (50.0) | 4 (25.0) | 128 (12.5) | ****154 (14.0)**** |\n| ****Quarantine status**** |   |   |   |   |   |\n| Quarantined at time of specimen collection | 17 (43.6) | 6 (33.3) | 3 (18.8) | 109 (10.6) | ****135 (12.3)**** |\n| Time between quarantine initiation to specimen collection, median days (range) | 1 (0–8) | 3\\.5 (0–6) | 1 (0–4) | 4 (0–28) | ****4 (0–28)**** |\n| ****Reported symptoms**** |   |   |   |   |   |\n| No current symptoms | 7 (17.9) | 10 (55.6) | 14 (87.5) | 840 (82.0) | ****871 (79.3)**** |\n| One or more symptoms in the past 14 days | 2 (28.6) | 1 (10.0) | 0 (0) | 50 (6.0) | ****53 (6.1)**** |\n| No symptoms in the past 14 days | 5 (71.4) | 9 (90.0) | 14 (100.0) | 790 (94.0) | ****818 (93.9)**** |\n| One or more current symptoms | 32 (82.1) | 8 (44.4) | 2 (12.5) | 185 (18.0) | 227 (20.7) |\n| Nasal congestion | 24 (75.0) | 2 (25.0) | 1 (50.0) | 87 (47.0) | ****114 (50.2)**** |\n| Sore throat | 12 (37.5) | 5 (62.5) | 1 (50.0) | 79 (42.7) | ****97 (42.7)**** |\n| Headache | 17 (53.1) | 3 (37.5) | 1 (50.0) | 66 (35.7) | ****87 (38.3)**** |\n| Cough | 18 (56.3) | 6 (75.0) | 1 (50.0) | 45 (24.3) | ****70 (30.8)**** |\n| Fatigue | 14 (43.8) | 3 (37.5) | 1 (50.0) | 42 (22.7) | ****60 (26.4)**** |\n| Muscle aches | 11 (34.4) | 2 (25.0) | 0 (0) | 30 (16.2) | ****43 (18.9)**** |\n| Shortness of breath | 7 (21.9) | 1 (12.5) | 0 (0) | 16 (8.6) | ****24 (10.6)**** |\n| Chills | 4 (12.5) | 0 (0) | 0 (0) | 14 (7.6) | ****18 (7.9)**** |\n| Diarrhea | 3 (9.4) | 0 (0) | 0 (0) | 15 (8.1) | ****18 (7.9)**** |\n| Nausea or vomiting | 3 (9.4) | 0 (0) | 0 (0) | 14 (7.6) | ****17 (7.5)**** |\n| Loss of taste | 8 (25.0) | 2 (25.0) | 1 (50.0) | 3 (1.6) | ****14 (6.2)**** |\n| Loss of smell | 8 (25.0) | 2 (25.0) | 1 (50.0) | 2 (1.1) | ****13 (5.7)**** |\n| Fever | 6 (18.8) | 0 (0) | 0 (0) | 5 (2.7) | ****11 (4.8)**** |\n| Difficulty breathing | 3 (9.4) | 0 (0) | 0 (0) | 8 (4.3) | ****11 (4.8)**** |\n| Abdominal pain | 1 (3.1) | 0 (0) | 0 (0) | 6 (3.2) | ****7 (3.1)**** |\n| Rigors | 0 (0) | 0 (0) | 0 (0) | 0 (0) | ****0 (0.0)**** |\n| Other reported symptoms\\*\\*\\* | 1 (3.1) | 0 (0) | 0 (0) | 4 (2.2) | ****5 (2.2)**** |\n| ****Symptom onset date reported**** | 31 (96.9) | 8 (100.0) | 2 (100.0) | 169 (91.4) | ****210 (92.5)**** |\n| ≤5 days between reported symptom onset and specimen collection | 23 (74.2) | 8 (100.0) | 1 (50.0) | 120 (71.0) | ****152 (72.4)**** |\n\n\\* Includes 57 participants who received multiple tests and were included more than once in the analysis.  \n † True positive = antigen-positive and real-time RT-PCR–positive; false negative = antigen-negative and real-time RT-PCR–positive; false positive = antigen-positive and real-time RT-PCR–negative; true negative = antigen-negative and real-time RT-PCR–negative; these definitions do not reflect results from viral culture.  \n § At university A, real-time RT-PCR was performed using the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2.  \n ¶ At university B, real-time RT-PCR was performed using Thermo Fisher Scientific’s TaqPath COVID-19 Combo Kit for detection of SARS-CoV-2.  \n \\*\\* One university staff member’s child aged 15 years. All other participants were aged ≥17 years.  \n †† Non-Hispanic ethnicity represented for all White, Black\/African-American, Asian\/Pacific Islander, American Indian\/Alaska Native, Other\/Unknown\/Multiple races.  \n §§ Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members.  \n ¶¶ Ever in close contact was defined as within 6 feet for ≥15 minutes of a person with a diagnosis of COVID-19.  \n \\*\\*\\* Other reported symptoms included allergies, cough that is not dry, and difficulty breathing from anxiety.\n\n| Antigen test result | Real-time RT-PCR result, no. |   |   |   |   |   |\n|---|---|---|---|---|---|---|\n| Asymptomatic (N = 871) | Symptomatic\\* (N = 227) |   |   |   |   |   |\n| Positive | Negative | Total | Positive | Negative | Total |   |\n| Positive | 7 | 14 | ****21**** | 32 | 2 | ****34**** |\n| Negative | 10 | 840 | ****850**** | 8 | 185 | ****193**** |\n| ****Total**** | ****17**** | ****854**** | ****871**** | ****40**** | ****187**** | ****227**** |\n| ****Test evaluation, % (95% CI)**** |   |   |   |   |   |   |\n| Sensitivity | 41\\.2 (18.4–67.1) | 80\\.0 (64.4–90.9) |   |   |   |   |\n| Specificity | 98\\.4 (97.3–99.1) | 98\\.9 (96.2–99.9) |   |   |   |   |\n| Positive predictive value | 33\\.3 (14.6–57.0) | 94\\.1 (80.3–99.3) |   |   |   |   |\n| Negative predictive value | 98\\.8 (97.8–99.4) | 95\\.9 (92.0–98.2) |   |   |   |   |\n\n****Abbreviation:**** CI = confidence interval.  \n \\* One or more symptoms reported.\n\n##### [![Return to your place in the text](https:\/\/www.cdc.gov\/images\/arrow_up.gif)](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/mm695152a3.htm#F1_up)**FIGURE**. **Viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) results (n = 69),\\* by cycle threshold (Ct) value† and the interval between specimen collection and reported symptom onset or asymptomatic status — university A, Wisconsin, September–October 2020**\n![The figure is a scatterplot showing viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction results (n = 69), by cycle threshold value and the interval between specimen collection and reported symptom onset or asymptomatic status at university A in Wisconsin during September–October 2020.](https:\/\/www.cdc.gov\/mmwr\/volumes\/69\/wr\/figures\/mm695152a3-F.gif?_=47024)\n\n\\* n = 30 antigen- and culture-positive; n = 22 antigen-positive and culture-negative; n = 15 antigen- and culture-negative; n = two antigen- negative and culture-positive.\n\n† Ct values represent cycle thresholds for the N1 target probe during SARS-CoV-2 real-time RT-PCR; Ct values are represented on the y-axis in descending order to indicate that lower Ct values represent higher levels of RNA in the specimen.\n\n**Suggested citation for this article:** Pray IW, Ford L, Cole D, et al. Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020. MMWR Morb Mortal Wkly Rep 2021;69:1642–1647. DOI: <http:\/\/dx.doi.org\/10.15585\/mmwr.mm695152a3>.\n\n*MMWR* and *Morbidity and Mortality Weekly Report* are service marks of the U.S. Department of Health and Human Services.  \n Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services.   \nReferences to non-CDC sites on the Internet are provided as a service to *MMWR* readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. 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Meta Title	Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020 \| MMWR
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Boilerpipe Text	Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020 Weekly / January 1, 2021 / 69(5152);1642–1647 Please note: This report has been corrected. Ian W. Pray, PhD 1 ,2 ,3, ; Laura Ford, PhD 1 ,2, ; Devlin Cole, MD 3 ,4 ; Christine Lee, PhD 1 ,5 ; John Paul Bigouette, PhD 1 ,2 ; Glen R. Abedi, MPH 1 ; Dena Bushman, MSN, MPH 1 ,2 ; Miranda J. Delahoy, PhD 1 ,2 ; Dustin Currie, PhD 1 ,2 ; Blake Cherney, MS 1 ; Marie Kirby, PhD 1 ; Geroncio Fajardo, MD 1 ; Motria Caudill, PhD 1 ,6 ; Kimberly Langolf, MS 7 ; Juliana Kahrs, MS 7 ; Patrick Kelly, MD 4 ,8 ; Collin Pitts, MD 4 ,8 ; Ailam Lim, PhD 9 ; Nicole Aulik, PhD 9 ; Azaibi Tamin, PhD 1 ; Jennifer L. Harcourt, PhD 1 ; Krista Queen, PhD 1 ; Jing Zhang, PhD 1 ; Brett Whitaker, PhD 1 ; Hannah Browne 1 ; Magdalena Medrzycki, PhD 1 ; Patricia Shewmaker, PhD 1 ; Jennifer Folster, PhD 1 ; Bettina Bankamp, PhD 1 ; Michael D. Bowen, PhD 1 ; Natalie J. Thornburg, PhD 1 ; Kimberly Goffard, MBA 10 ; Brandi Limbago, PhD 1 ; Allen Bateman, PhD 7 ,11 ; Jacqueline E. Tate, PhD 1 ; Douglas Gieryn 10 ; Hannah L. Kirking, MD 1 ; Ryan Westergaard, MD, PhD 3 ,4 ; Marie Killerby, VetMB 1 ; CDC COVID-19 Surge Laboratory Group ( View author affiliations ) View suggested citation Summary What is already known about this topic? Antigen tests for SARS-CoV-2 are inexpensive and can return results within 15 minutes, but test performance data in asymptomatic and symptomatic persons are limited. What is added by this report? Compared with real-time reverse transcription–polymerase chain reaction (RT-PCR) testing, the Sofia antigen test had a sensitivity of 80.0% and specificity of 98.9% among symptomatic persons; accuracy was lower (sensitivity 41.2% and specificity 98.4%) when used for screening of asymptomatic persons. What are the implications for public health practice? To account for reduced antigen test accuracy, confirmatory testing with a nucleic acid amplification test (e.g., RT-PCR) should be considered after negative antigen test results in symptomatic persons and positive antigen test results in asymptomatic persons. Altmetric: Mendeley (295) Discussion The Sofia SARS Antigen FIA received FDA EUA on May 8, 2020, for use in symptomatic persons within 5 days of symptom onset ( 2 ). In this investigation, among persons reporting COVID-19–compatible symptoms at specimen collection, the test was less accurate (sensitivity = 80.0%; specificity = 98.9%) than reported in the FDA EUA (sensitivity = 96.7%; specificity = 100%) ( 2 ). Two of eight specimens from symptomatic persons that had false-negative antigen test results were positive by viral culture, indicating that potentially infectious persons might not be detected by antigen testing. To reduce the impact of false-negative antigen test results, confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, should be considered following negative antigen test results in symptomatic persons ( 1 ). Among asymptomatic participants, antigen test sensitivity was 41.2%, specificity was 98.4%, and PPV in this population was 33.3%. This low PPV was observed despite a relatively high prevalence of SARS-CoV-2 in this population (5.2% prevalence overall; 2.0% among asymptomatic persons), suggesting that PPV could be even lower when using this antigen test among populations with lower expected SARS-CoV-2 prevalence. To account for false-positive results when using antigen tests for asymptomatic screening, confirmatory NAAT testing should be considered following positive antigen test results in asymptomatic persons, particularly when pretest probability of SARS-CoV-2 infection is low ( 1 ). The NPV of antigen testing among asymptomatic participants was 98.8%, and virus was not cultured from asymptomatic participants with antigen-negative results, indicating that asymptomatic persons with negative antigen results are unlikely to be infected with SARS-CoV-2 and would not require confirmatory NAAT ( 1 ). The findings in this report are subject to at least four limitations. First, participants were predominantly young adults in university settings where ongoing serial testing was being conducted. Antigen test performance might differ in other populations with different characteristics and testing schedules. Second, given the limitations of RT-PCR, some false-positive antigen test results might represent true infections not identified by RT-PCR. Third, the ability to recover infectious virus in culture is limited and decreases for specimens with higher Ct values ( 8 ); a lack of virus recovery by culture does not indicate that a person is not infectious. Finally, this investigation evaluated the Sofia SARS Antigen FIA, and cannot be generalized to other FDA-authorized SARS-CoV-2 antigen tests. Serial testing of asymptomatic and symptomatic persons has been proposed for prevention and control of SARS-CoV-2 transmission ( 9 , 10 ) and is currently being implemented at U.S. colleges and universities and in other congregate settings ( 3 – 5 ). Despite reduced sensitivity compared with real-time RT-PCR, the use of antigen tests for serial testing in these settings, particularly when RT-PCR tests are not available or have a prolonged turnaround time, might still allow rapid identification of infectious persons and control of outbreaks ( 1 ). However, antigen-based testing strategies should account for the lower sensitivity and lower PPV when used for asymptomatic screening by considering confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, after a positive antigen test result in an asymptomatic person. Confirmatory testing should also be considered following a negative antigen test result in a person experiencing COVID-19–compatible symptoms. All persons with negative antigen test results should continue to take measures to prevent SARS-CoV-2 transmission, including wearing a mask, reducing contact with nonhousehold members, and getting tested if they experience symptoms or have close contact with someone who has COVID-19. ††† Symptomatic persons with negative antigen test results should continue to follow CDC guidance §§§ for persons who might have COVID-19, including staying home except to get medical care and protecting household members by staying in a separate room, wearing a mask indoors, washing hands often, and frequently disinfecting surfaces. Acknowledgments Edward Samuel Rivera, Daniel J. O’Donnell, University of Wisconsin-Oshkosh; Margaret Okomo-Adhiambo, Umesh Parashar, Paul Rota, Lauren Franco, Gerardo Garcia-Lerma, CDC; Neeti Dahal, Wisconsin Veterinary Diagnostic Laboratory-Wisconsin State Laboratory of Hygiene COVID Laboratory, University of Wisconsin-Madison. CDC COVID-19 Surge Laboratory Group Baoming Jiang, CDC; Jan Vinjé, CDC; Amy L. Hopkins, CDC; Eric Katz, CDC; Leslie Barclay, CDC; Mathew Esona, CDC; Rashi Gautam, CDC; Slavica Mijatovic-Rustempasic, CDC; Sung-Sil Moon, CDC; Theresa Bessey, CDC; Preeti Chhabra, CDC; Sarah L. Smart, CDC; Raydel Anderson, CDC; Kay W. Radford, CDC; Gimin Kim, CDC; Dexter Thompson, CDC; Congrong Miao, CDC; Min-hsin Chen, CDC; Lalitha Gade, CDC; Renee Galloway, CDC; Kashif Sahibzada, CDC; Nhien M. Tran, CDC; Srinivasan Velusamy, CDC; HaoQiang Zheng, CDC; Kenny Nguyen, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Claire Hartloge, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Brent Jenkins, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Phili Wong, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 1 CDC COVID-19 Response Team; 2 Epidemic Intelligence Service, CDC; 3 Wisconsin Department of Health Services; 4 School of Medicine and Public Health, University of Wisconsin-Madison; 5 Laboratory Leadership Service, CDC; 6 Agency for Toxic Substances and Disease Registry, Atlanta, Georgia; 7 University of Wisconsin-Oshkosh; 8 University Health Services, University of Wisconsin-Madison; 9 Wisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison; 10 Winnebago County Health Department, Oshkosh, Wisconsin; 11 Wisconsin State Laboratory of Hygiene. All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed. * These authors contributed equally to this report. † Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members. § Symptom list was based on the interim position statement for COVID-19 case definitions from the Council of State and Territorial Epidemiologists, updated August 7, 2020. Clinical criteria for COVID-19 included fever, cough, shortness of breath, fatigue, sore throat, headache, muscle aches, chills, nasal congestion, difficulty breathing, diarrhea, nausea, vomiting, abdominal pain, rigors, loss of taste, and loss of smell. https://cdn.ymaws.com/www.cste.org/resource/resmgr/ps/positionstatement2020/Interim-20-ID-02_COVID-19.pdf . ¶ Recent exposure was defined as being within 6 feet of a person with a COVID-19 diagnosis for ≥15 minutes in the past 14 days. https://www.fda.gov/media/137885/download . †† Specimens were used to perform a limiting-dilution inoculation of Vero CCL-81 cells, and cultures showing evidence of cytopathic effect (CPE) were tested by real-time RT-PCR for the presence of SARS-CoV-2 RNA. Viral recovery was defined as any culture in which the first passage had an N1 Ct at least twofold lower than the corresponding clinical specimen. §§ Ct values from real-time RT-PCR were only compared for specimens collected at university A that were analyzed with the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2. ¶¶ 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq. * The participant with a false-negative result 2 days after symptom onset had a repeat specimen 2 days later; the results of testing were positive by antigen test and by real-time RT-PCR. ††† https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html . §§§ https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/steps-when-sick.html . References CDC. Coronavirus disease 2019 (COVID-19): interim guidance for antigen testing for SARS-CoV-2. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html Food and Drug Administration. In vitro diagnostics EUAs. Silver Spring, MD: US Department of Health and Human Services, Food and Drug Administration; 2020. https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/vitro-diagnostics-euas CDC. Coronavirus disease 2019 (COVID-19): guidance for testing, screening, and outbreak response for institutions of higher education (IHEs). Atlanta, GA: US Department of Health and Human Services, CDC; 2020. https://www.cdc.gov/coronavirus/2019-ncov/community/colleges-universities/ihe-testing.html CDC. Coronavirus disease 2019 (COVID-19): testing guidelines for nursing homes. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. https://www.cdc.gov/coronavirus/2019-ncov/hcp/nursing-homes-testing.html CDC. Coronavirus disease 2019 (COVID-19): interim considerations for SARS-CoV-2 testing in correctional and detention facilities. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. https://www.cdc.gov/coronavirus/2019-ncov/community/correction-detention/testing.html Lu X, Wang L, Sakthivel SK, et al. US CDC real-time reverse transcription PCR panel for detection of severe acute respiratory syndrome coronavirus 2. Emerg Infect Dis 2020;26:1654–65. CrossRef PubMed Harcourt J, Tamin A, Lu X, et al. Severe acute respiratory syndrome coronavirus 2 from patient with coronavirus disease, United States. Emerg Infect Dis 2020;26:1266–73. CrossRef PubMed Gniazdowski V, Morris CP, Wohl S, et al. Repeat COVID-19 molecular testing: correlation of SARS-CoV-2 culture with molecular assays and cycle thresholds. Clin Infect Dis 2020;ciaa1616. CrossRef PubMed Walke HT, Honein MA, Redfield RR. Preventing and responding to COVID-19 on college campuses. JAMA 2020;324:1727–8. CrossRef PubMed Paltiel AD, Zheng A, Walensky RP. Assessment of SARS-CoV-2 screening strategies to permit the safe reopening of college campuses in the United States. JAMA Netw Open 2020;3:e2016818. CrossRef PubMed TABLE 1. Characteristics and symptoms of persons providing paired nasal swabs (N = 1,098),* by results for SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) and Sofia SARS Antigen Fluorescent Immunoassay testing† — two universities, Wisconsin, September–October 2020 Characteristic No (%) True positives (N = 39) False negatives (N = 18) False positives (N = 16) True negatives (N = 1,025) Total (N = 1,098) Testing site University A § 37 (94.9) 17 (94.4) 15 (93.8) 982 (95.8) 1,051 (95.7) University B ¶ 2 (5.1) 1 (5.6) 1 (6.3) 43 (4.2) 47 (4.3) Sex Male 16 (41.0) 9 (50.0) 12 (75.0) 416 (40.6) 453 (41.3) Female 23 (59.0) 9 (50.0) 4 (25.0) 609 (59.4) 645 (58.7) Age group (yrs) 15–24 35 (89.7) 16 (88.9) 11 (68.8) 909 (88.7) 971 (88.4) ≥25 4 (10.3) 2 (11.1) 5 (31.3) 116 (11.3) 127 (11.6) Race/Ethnicity †† White 31 (79.5) 17 (94.4) 12 (75.0) 857 (83.6) 917 (83.5) Hispanic/Latino 6 (15.4) 0 (0) 1 (6.3) 54 (5.3) 61 (5.6) Black/African-American 0 (0) 1 (5.6) 2 (12.5) 26 (2.5) 29 (2.6) Asian/Pacific Islander 0 (0) 0 (0) 0 (0) 49 (4.8) 49 (4.5) American Indian/Alaska Native 0 (0) 0 (0) 0 (0) 3 (0.3) 3 (0.3) Other/Unknown/Multiple races 2 (5.1) 0 (0) 1 (6.3) 36 (3.5) 39 (3.6) University status Student 35 (89.7) 17 (94.4) 13 (81.3) 929 (90.6) 994 (90.5) Faculty or staff member 4 (10.3) 1 (5.6) 3 (18.8) 74 (7.2) 82 (7.5) Other affiliate or unknown §§ 0 (0) 0 (0) 0 (0) 22 (2.2) 22 (2.0) Exposure ¶¶ to a COVID-19 case Been in close contact in the past 14 days 13 (33.3) 9 (50.0) 4 (25.0) 128 (12.5) 154 (14.0) Quarantine status Quarantined at time of specimen collection 17 (43.6) 6 (33.3) 3 (18.8) 109 (10.6) 135 (12.3) Time between quarantine initiation to specimen collection, median days (range) 1 (0–8) 3.5 (0–6) 1 (0–4) 4 (0–28) 4 (0–28) Reported symptoms No current symptoms 7 (17.9) 10 (55.6) 14 (87.5) 840 (82.0) 871 (79.3) One or more symptoms in the past 14 days 2 (28.6) 1 (10.0) 0 (0) 50 (6.0) 53 (6.1) No symptoms in the past 14 days 5 (71.4) 9 (90.0) 14 (100.0) 790 (94.0) 818 (93.9) One or more current symptoms 32 (82.1) 8 (44.4) 2 (12.5) 185 (18.0) 227 (20.7) Nasal congestion 24 (75.0) 2 (25.0) 1 (50.0) 87 (47.0) 114 (50.2) Sore throat 12 (37.5) 5 (62.5) 1 (50.0) 79 (42.7) 97 (42.7) Headache 17 (53.1) 3 (37.5) 1 (50.0) 66 (35.7) 87 (38.3) Cough 18 (56.3) 6 (75.0) 1 (50.0) 45 (24.3) 70 (30.8) Fatigue 14 (43.8) 3 (37.5) 1 (50.0) 42 (22.7) 60 (26.4) Muscle aches 11 (34.4) 2 (25.0) 0 (0) 30 (16.2) 43 (18.9) Shortness of breath 7 (21.9) 1 (12.5) 0 (0) 16 (8.6) 24 (10.6) Chills 4 (12.5) 0 (0) 0 (0) 14 (7.6) 18 (7.9) Diarrhea 3 (9.4) 0 (0) 0 (0) 15 (8.1) 18 (7.9) Nausea or vomiting 3 (9.4) 0 (0) 0 (0) 14 (7.6) 17 (7.5) Loss of taste 8 (25.0) 2 (25.0) 1 (50.0) 3 (1.6) 14 (6.2) Loss of smell 8 (25.0) 2 (25.0) 1 (50.0) 2 (1.1) 13 (5.7) Fever 6 (18.8) 0 (0) 0 (0) 5 (2.7) 11 (4.8) Difficulty breathing 3 (9.4) 0 (0) 0 (0) 8 (4.3) 11 (4.8) Abdominal pain 1 (3.1) 0 (0) 0 (0) 6 (3.2) 7 (3.1) Rigors 0 (0) 0 (0) 0 (0) 0 (0) 0 (0.0) Other reported symptoms* 1 (3.1) 0 (0) 0 (0) 4 (2.2) 5 (2.2) Symptom onset date reported 31 (96.9) 8 (100.0) 2 (100.0) 169 (91.4) 210 (92.5) ≤5 days between reported symptom onset and specimen collection 23 (74.2) 8 (100.0) 1 (50.0) 120 (71.0) 152 (72.4) * Includes 57 participants who received multiple tests and were included more than once in the analysis. † True positive = antigen-positive and real-time RT-PCR–positive; false negative = antigen-negative and real-time RT-PCR–positive; false positive = antigen-positive and real-time RT-PCR–negative; true negative = antigen-negative and real-time RT-PCR–negative; these definitions do not reflect results from viral culture. § At university A, real-time RT-PCR was performed using the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2. ¶ At university B, real-time RT-PCR was performed using Thermo Fisher Scientific’s TaqPath COVID-19 Combo Kit for detection of SARS-CoV-2. One university staff member’s child aged 15 years. All other participants were aged ≥17 years. †† Non-Hispanic ethnicity represented for all White, Black/African-American, Asian/Pacific Islander, American Indian/Alaska Native, Other/Unknown/Multiple races. §§ Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members. ¶¶ Ever in close contact was defined as within 6 feet for ≥15 minutes of a person with a diagnosis of COVID-19. * Other reported symptoms included allergies, cough that is not dry, and difficulty breathing from anxiety. TABLE 2. Sensitivity, specificity, positive predictive value, and negative predictive value of Sofia SARS Antigen Fluorescent Immunoassay compared with real-time reverse transcription–polymerase chain reaction (RT-PCR) among asymptomatic and symptomatic persons — two universities, Wisconsin, September–October 2020 Antigen test result Real-time RT-PCR result, no. Asymptomatic (N = 871) Symptomatic* (N = 227) Positive Negative Total Positive Negative Total Positive 7 14 21 32 2 34 Negative 10 840 850 8 185 193 Total 17 854 871 40 187 227 Test evaluation, % (95% CI) Sensitivity 41.2 (18.4–67.1) 80.0 (64.4–90.9) Specificity 98.4 (97.3–99.1) 98.9 (96.2–99.9) Positive predictive value 33.3 (14.6–57.0) 94.1 (80.3–99.3) Negative predictive value 98.8 (97.8–99.4) 95.9 (92.0–98.2) Abbreviation: CI = confidence interval. * One or more symptoms reported. FIGURE . Viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) results (n = 69),* by cycle threshold (Ct) value† and the interval between specimen collection and reported symptom onset or asymptomatic status — university A, Wisconsin, September–October 2020 * n = 30 antigen- and culture-positive; n = 22 antigen-positive and culture-negative; n = 15 antigen- and culture-negative; n = two antigen- negative and culture-positive. † Ct values represent cycle thresholds for the N1 target probe during SARS-CoV-2 real-time RT-PCR; Ct values are represented on the y-axis in descending order to indicate that lower Ct values represent higher levels of RNA in the specimen. Suggested citation for this article: Pray IW, Ford L, Cole D, et al. Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020. MMWR Morb Mortal Wkly Rep 2021;69:1642–1647. DOI: http://dx.doi.org/10.15585/mmwr.mm695152a3 . MMWR and Morbidity and Mortality Weekly Report are service marks of the U.S. Department of Health and Human Services. Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services. References to non-CDC sites on the Internet are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. URL addresses listed in MMWR were current as of the date of publication. All HTML versions of MMWR articles are generated from final proofs through an automated process. 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) [Morbidity and Mortality Weekly Report (MMWR)](https://www.cdc.gov/mmwr/index.html) [Morbidity and Mortality Weekly Report (MMWR)](https://www.cdc.gov/mmwr/index.html) # Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020 Weekly / January 1, 2021 / 69(5152);1642–1647 [Print](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#print) Related Pages *Please note: This report has been corrected.* Ian W. Pray, PhD1,2,3,\; Laura Ford, PhD1,2,\; Devlin Cole, MD3,4; Christine Lee, PhD1,5; John Paul Bigouette, PhD1,2; Glen R. Abedi, MPH1; Dena Bushman, MSN, MPH1,2; Miranda J. Delahoy, PhD1,2; Dustin Currie, PhD1,2; Blake Cherney, MS1; Marie Kirby, PhD1; Geroncio Fajardo, MD1; Motria Caudill, PhD1,6; Kimberly Langolf, MS7; Juliana Kahrs, MS7; Patrick Kelly, MD4,8; Collin Pitts, MD4,8; Ailam Lim, PhD9; Nicole Aulik, PhD9; Azaibi Tamin, PhD1; Jennifer L. Harcourt, PhD1; Krista Queen, PhD1; Jing Zhang, PhD1; Brett Whitaker, PhD1; Hannah Browne1; Magdalena Medrzycki, PhD1; Patricia Shewmaker, PhD1; Jennifer Folster, PhD1; Bettina Bankamp, PhD1; Michael D. Bowen, PhD1; Natalie J. Thornburg, PhD1; Kimberly Goffard, MBA10; Brandi Limbago, PhD1; Allen Bateman, PhD7,11; Jacqueline E. Tate, PhD1; Douglas Gieryn10; Hannah L. Kirking, MD1; Ryan Westergaard, MD, PhD3,4; Marie Killerby, VetMB1; CDC COVID-19 Surge Laboratory Group ([View author affiliations](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#contribAff)) [View suggested citation](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#suggestedcitation) ### Summary What is already known about this topic? Antigen tests for SARS-CoV-2 are inexpensive and can return results within 15 minutes, but test performance data in asymptomatic and symptomatic persons are limited. What is added by this report? Compared with real-time reverse transcription–polymerase chain reaction (RT-PCR) testing, the Sofia antigen test had a sensitivity of 80.0% and specificity of 98.9% among symptomatic persons; accuracy was lower (sensitivity 41.2% and specificity 98.4%) when used for screening of asymptomatic persons. What are the implications for public health practice? To account for reduced antigen test accuracy, confirmatory testing with a nucleic acid amplification test (e.g., RT-PCR) should be considered after negative antigen test results in symptomatic persons and positive antigen test results in asymptomatic persons. Article Metrics ##### Altmetric: [![Article has an altmetric score of 2033](https://badges.altmetric.com/?size=128&score=2033&types=mbvcrtfd)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238) [See more details](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238) [News (43)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=news) [Blogs (7)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=blogs) [Policy documents (3)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=policy-documents) [X (2647)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=twitter) [Facebook (9)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=facebook) [Reddit (59)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=reddit) [Video (1)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=video) [Clinical guidelines (2)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=guidelines) [Podcasts (1)](https://www.altmetric.com/details.php?domain=www.cdc.gov&citation_id=96939238&tab=podcasts) Mendeley (295) [Figure](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#F1_down) Tables [Table 1](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#T1_down) [Table 2](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#T2_down) Related Materials - [PDF \[142K\]](https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm695152a3-H.pdf) [![The figure is a visual abstract describing that COVID-19 rapid tests are inexpensive and fast but sometimes give incorrect results.](https://www.cdc.gov/mmwr/volumes/69/wr/social-media/mm695152a3_RapidAntigenTestResultsCOVID19_IMAGE_01Jan21_1200x675.jpg?_=41053)\[JPG - 135 KB\]](https://www.cdc.gov/mmwr/volumes/69/wr/social-media/mm695152a3_RapidAntigenTestResultsCOVID19_IMAGE_01Jan21_1200x675.jpg) ## Discussion The Sofia SARS Antigen FIA received FDA EUA on May 8, 2020, for use in symptomatic persons within 5 days of symptom onset (2). In this investigation, among persons reporting COVID-19–compatible symptoms at specimen collection, the test was less accurate (sensitivity = 80.0%; specificity = 98.9%) than reported in the FDA EUA (sensitivity = 96.7%; specificity = 100%) (2). Two of eight specimens from symptomatic persons that had false-negative antigen test results were positive by viral culture, indicating that potentially infectious persons might not be detected by antigen testing. To reduce the impact of false-negative antigen test results, confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, should be considered following negative antigen test results in symptomatic persons (1). Among asymptomatic participants, antigen test sensitivity was 41.2%, specificity was 98.4%, and PPV in this population was 33.3%. This low PPV was observed despite a relatively high prevalence of SARS-CoV-2 in this population (5.2% prevalence overall; 2.0% among asymptomatic persons), suggesting that PPV could be even lower when using this antigen test among populations with lower expected SARS-CoV-2 prevalence. To account for false-positive results when using antigen tests for asymptomatic screening, confirmatory NAAT testing should be considered following positive antigen test results in asymptomatic persons, particularly when pretest probability of SARS-CoV-2 infection is low (1). The NPV of antigen testing among asymptomatic participants was 98.8%, and virus was not cultured from asymptomatic participants with antigen-negative results, indicating that asymptomatic persons with negative antigen results are unlikely to be infected with SARS-CoV-2 and would not require confirmatory NAAT (1). The findings in this report are subject to at least four limitations. First, participants were predominantly young adults in university settings where ongoing serial testing was being conducted. Antigen test performance might differ in other populations with different characteristics and testing schedules. Second, given the limitations of RT-PCR, some false-positive antigen test results might represent true infections not identified by RT-PCR. Third, the ability to recover infectious virus in culture is limited and decreases for specimens with higher Ct values (8); a lack of virus recovery by culture does not indicate that a person is not infectious. Finally, this investigation evaluated the Sofia SARS Antigen FIA, and cannot be generalized to other FDA-authorized SARS-CoV-2 antigen tests. Serial testing of asymptomatic and symptomatic persons has been proposed for prevention and control of SARS-CoV-2 transmission (9,10) and is currently being implemented at U.S. colleges and universities and in other congregate settings (3–5). Despite reduced sensitivity compared with real-time RT-PCR, the use of antigen tests for serial testing in these settings, particularly when RT-PCR tests are not available or have a prolonged turnaround time, might still allow rapid identification of infectious persons and control of outbreaks (1). However, antigen-based testing strategies should account for the lower sensitivity and lower PPV when used for asymptomatic screening by considering confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, after a positive antigen test result in an asymptomatic person. Confirmatory testing should also be considered following a negative antigen test result in a person experiencing COVID-19–compatible symptoms. All persons with negative antigen test results should continue to take measures to prevent SARS-CoV-2 transmission, including wearing a mask, reducing contact with nonhousehold members, and getting tested if they experience symptoms or have close contact with someone who has COVID-19.††† Symptomatic persons with negative antigen test results should continue to follow CDC guidance§§§ for persons who might have COVID-19, including staying home except to get medical care and protecting household members by staying in a separate room, wearing a mask indoors, washing hands often, and frequently disinfecting surfaces. [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) ### Acknowledgments Edward Samuel Rivera, Daniel J. O’Donnell, University of Wisconsin-Oshkosh; Margaret Okomo-Adhiambo, Umesh Parashar, Paul Rota, Lauren Franco, Gerardo Garcia-Lerma, CDC; Neeti Dahal, Wisconsin Veterinary Diagnostic Laboratory-Wisconsin State Laboratory of Hygiene COVID Laboratory, University of Wisconsin-Madison. ### CDC COVID-19 Surge Laboratory Group Baoming Jiang, CDC; Jan Vinjé, CDC; Amy L. Hopkins, CDC; Eric Katz, CDC; Leslie Barclay, CDC; Mathew Esona, CDC; Rashi Gautam, CDC; Slavica Mijatovic-Rustempasic, CDC; Sung-Sil Moon, CDC; Theresa Bessey, CDC; Preeti Chhabra, CDC; Sarah L. Smart, CDC; Raydel Anderson, CDC; Kay W. Radford, CDC; Gimin Kim, CDC; Dexter Thompson, CDC; Congrong Miao, CDC; Min-hsin Chen, CDC; Lalitha Gade, CDC; Renee Galloway, CDC; Kashif Sahibzada, CDC; Nhien M. Tran, CDC; Srinivasan Velusamy, CDC; HaoQiang Zheng, CDC; Kenny Nguyen, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Claire Hartloge, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Brent Jenkins, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Phili Wong, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) Corresponding author: Ian Pray, [ian.pray@dhs.wisconsin.gov](mailto:ian.pray@dhs.wisconsin.gov). [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) *** 1CDC COVID-19 Response Team; 2Epidemic Intelligence Service, CDC; 3Wisconsin Department of Health Services; 4School of Medicine and Public Health, University of Wisconsin-Madison; 5Laboratory Leadership Service, CDC; 6Agency for Toxic Substances and Disease Registry, Atlanta, Georgia; 7University of Wisconsin-Oshkosh; 8University Health Services, University of Wisconsin-Madison; 9Wisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison; 10Winnebago County Health Department, Oshkosh, Wisconsin; 11Wisconsin State Laboratory of Hygiene. [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed. [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) \* These authors contributed equally to this report. † Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members. § Symptom list was based on the interim position statement for COVID-19 case definitions from the Council of State and Territorial Epidemiologists, updated August 7, 2020. Clinical criteria for COVID-19 included fever, cough, shortness of breath, fatigue, sore throat, headache, muscle aches, chills, nasal congestion, difficulty breathing, diarrhea, nausea, vomiting, abdominal pain, rigors, loss of taste, and loss of smell. <https://cdn.ymaws.com/www.cste.org/resource/resmgr/ps/positionstatement2020/Interim-20-ID-02_COVID-19.pdf>. ¶ Recent exposure was defined as being within 6 feet of a person with a COVID-19 diagnosis for ≥15 minutes in the past 14 days. \\ <https://www.fda.gov/media/137885/download>. †† Specimens were used to perform a limiting-dilution inoculation of Vero CCL-81 cells, and cultures showing evidence of cytopathic effect (CPE) were tested by real-time RT-PCR for the presence of SARS-CoV-2 RNA. Viral recovery was defined as any culture in which the first passage had an N1 Ct at least twofold lower than the corresponding clinical specimen. §§ Ct values from real-time RT-PCR were only compared for specimens collected at university A that were analyzed with the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2. ¶¶ 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq. \\\* The participant with a false-negative result 2 days after symptom onset had a repeat specimen 2 days later; the results of testing were positive by antigen test and by real-time RT-PCR. ††† <https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html>. §§§ <https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/steps-when-sick.html>. [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) ## References 1. CDC. Coronavirus disease 2019 (COVID-19): interim guidance for antigen testing for SARS-CoV-2. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html> 2. Food and Drug Administration. In vitro diagnostics EUAs. Silver Spring, MD: US Department of Health and Human Services, Food and Drug Administration; 2020. <https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/vitro-diagnostics-euas> 3. CDC. Coronavirus disease 2019 (COVID-19): guidance for testing, screening, and outbreak response for institutions of higher education (IHEs). Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/community/colleges-universities/ihe-testing.html> 4. CDC. Coronavirus disease 2019 (COVID-19): testing guidelines for nursing homes. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/hcp/nursing-homes-testing.html> 5. CDC. Coronavirus disease 2019 (COVID-19): interim considerations for SARS-CoV-2 testing in correctional and detention facilities. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/community/correction-detention/testing.html> 6. Lu X, Wang L, Sakthivel SK, et al. US CDC real-time reverse transcription PCR panel for detection of severe acute respiratory syndrome coronavirus 2. Emerg Infect Dis 2020;26:1654–65. [CrossRef](http://dx.doi.org/10.3201/eid2608.201246) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/32396505) 7. Harcourt J, Tamin A, Lu X, et al. Severe acute respiratory syndrome coronavirus 2 from patient with coronavirus disease, United States. Emerg Infect Dis 2020;26:1266–73. [CrossRef](http://dx.doi.org/10.3201/eid2606.200516) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/32160149) 8. Gniazdowski V, Morris CP, Wohl S, et al. Repeat COVID-19 molecular testing: correlation of SARS-CoV-2 culture with molecular assays and cycle thresholds. Clin Infect Dis 2020;ciaa1616. [CrossRef](http://dx.doi.org/10.1093/cid/ciaa1616) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/33104776) 9. Walke HT, Honein MA, Redfield RR. Preventing and responding to COVID-19 on college campuses. JAMA 2020;324:1727–8. [CrossRef](http://dx.doi.org/10.1001/jama.2020.20027) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/32991681) 10. Paltiel AD, Zheng A, Walensky RP. Assessment of SARS-CoV-2 screening strategies to permit the safe reopening of college campuses in the United States. JAMA Netw Open 2020;3:e2016818. [CrossRef](http://dx.doi.org/10.1001/jamanetworkopen.2020.16818) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/32735339) [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) \| Characteristic \| No (%) \| \| \| \| \| \|---\|---\|---\|---\|---\|---\| \| True positives (N = 39) \| False negatives (N = 18) \| False positives (N = 16) \| True negatives (N = 1,025) \| Total (N = 1,098) \| \| \| **Testing site \| \| \| \| \| \| \| University A§ \| 37 (94.9) \| 17 (94.4) \| 15 (93.8) \| 982 (95.8) \| 1,051 (95.7) \| \| University B¶ \| 2 (5.1) \| 1 (5.6) \| 1 (6.3) \| 43 (4.2) \| 47 (4.3) \| \| Sex \| \| \| \| \| \| \| Male \| 16 (41.0) \| 9 (50.0) \| 12 (75.0) \| 416 (40.6) \| 453 (41.3) \| \| Female \| 23 (59.0) \| 9 (50.0) \| 4 (25.0) \| 609 (59.4) \| 645 (58.7) \| \| Age group (yrs)** \| \| \| \| \| \| \| 15–24\\ \| 35 (89.7) \| 16 (88.9) \| 11 (68.8) \| 909 (88.7) \| **971 (88.4) \| \| ≥25 \| 4 (10.3) \| 2 (11.1) \| 5 (31.3) \| 116 (11.3) \| 127 (11.6) \| \| Race/Ethnicity†† \| \| \| \| \| \| \| White \| 31 (79.5) \| 17 (94.4) \| 12 (75.0) \| 857 (83.6) \| 917 (83.5) \| \| Hispanic/Latino \| 6 (15.4) \| 0 (0) \| 1 (6.3) \| 54 (5.3) \| 61 (5.6) \| \| Black/African-American \| 0 (0) \| 1 (5.6) \| 2 (12.5) \| 26 (2.5) \| 29 (2.6) \| \| Asian/Pacific Islander \| 0 (0) \| 0 (0) \| 0 (0) \| 49 (4.8) \| 49 (4.5) \| \| American Indian/Alaska Native \| 0 (0) \| 0 (0) \| 0 (0) \| 3 (0.3) \| 3 (0.3) \| \| Other/Unknown/Multiple races \| 2 (5.1) \| 0 (0) \| 1 (6.3) \| 36 (3.5) \| 39 (3.6) \| \| University status \| \| \| \| \| \| \| Student \| 35 (89.7) \| 17 (94.4) \| 13 (81.3) \| 929 (90.6) \| 994 (90.5) \| \| Faculty or staff member \| 4 (10.3) \| 1 (5.6) \| 3 (18.8) \| 74 (7.2) \| 82 (7.5) \| \| Other affiliate or unknown§§ \| 0 (0) \| 0 (0) \| 0 (0) \| 22 (2.2) \| 22 (2.0) \| \| Exposure¶¶ to a COVID-19 case \| \| \| \| \| \| \| Been in close contact in the past 14 days \| 13 (33.3) \| 9 (50.0) \| 4 (25.0) \| 128 (12.5) \| 154 (14.0) \| \| Quarantine status \| \| \| \| \| \| \| Quarantined at time of specimen collection \| 17 (43.6) \| 6 (33.3) \| 3 (18.8) \| 109 (10.6) \| 135 (12.3) \| \| Time between quarantine initiation to specimen collection, median days (range) \| 1 (0–8) \| 3\.5 (0–6) \| 1 (0–4) \| 4 (0–28) \| 4 (0–28) \| \| Reported symptoms \| \| \| \| \| \| \| No current symptoms \| 7 (17.9) \| 10 (55.6) \| 14 (87.5) \| 840 (82.0) \| 871 (79.3) \| \| One or more symptoms in the past 14 days \| 2 (28.6) \| 1 (10.0) \| 0 (0) \| 50 (6.0) \| 53 (6.1) \| \| No symptoms in the past 14 days \| 5 (71.4) \| 9 (90.0) \| 14 (100.0) \| 790 (94.0) \| 818 (93.9) \| \| One or more current symptoms \| 32 (82.1) \| 8 (44.4) \| 2 (12.5) \| 185 (18.0) \| 227 (20.7) \| \| Nasal congestion \| 24 (75.0) \| 2 (25.0) \| 1 (50.0) \| 87 (47.0) \| 114 (50.2) \| \| Sore throat \| 12 (37.5) \| 5 (62.5) \| 1 (50.0) \| 79 (42.7) \| 97 (42.7) \| \| Headache \| 17 (53.1) \| 3 (37.5) \| 1 (50.0) \| 66 (35.7) \| 87 (38.3) \| \| Cough \| 18 (56.3) \| 6 (75.0) \| 1 (50.0) \| 45 (24.3) \| 70 (30.8) \| \| Fatigue \| 14 (43.8) \| 3 (37.5) \| 1 (50.0) \| 42 (22.7) \| 60 (26.4) \| \| Muscle aches \| 11 (34.4) \| 2 (25.0) \| 0 (0) \| 30 (16.2) \| 43 (18.9) \| \| Shortness of breath \| 7 (21.9) \| 1 (12.5) \| 0 (0) \| 16 (8.6) \| 24 (10.6) \| \| Chills \| 4 (12.5) \| 0 (0) \| 0 (0) \| 14 (7.6) \| 18 (7.9) \| \| Diarrhea \| 3 (9.4) \| 0 (0) \| 0 (0) \| 15 (8.1) \| 18 (7.9) \| \| Nausea or vomiting \| 3 (9.4) \| 0 (0) \| 0 (0) \| 14 (7.6) \| 17 (7.5) \| \| Loss of taste \| 8 (25.0) \| 2 (25.0) \| 1 (50.0) \| 3 (1.6) \| 14 (6.2) \| \| Loss of smell \| 8 (25.0) \| 2 (25.0) \| 1 (50.0) \| 2 (1.1) \| 13 (5.7) \| \| Fever \| 6 (18.8) \| 0 (0) \| 0 (0) \| 5 (2.7) \| 11 (4.8) \| \| Difficulty breathing \| 3 (9.4) \| 0 (0) \| 0 (0) \| 8 (4.3) \| 11 (4.8) \| \| Abdominal pain \| 1 (3.1) \| 0 (0) \| 0 (0) \| 6 (3.2) \| 7 (3.1) \| \| Rigors \| 0 (0) \| 0 (0) \| 0 (0) \| 0 (0) \| 0 (0.0)** \| \| Other reported symptoms\\\* \| 1 (3.1) \| 0 (0) \| 0 (0) \| 4 (2.2) \| **5 (2.2) \| \| Symptom onset date reported \| 31 (96.9) \| 8 (100.0) \| 2 (100.0) \| 169 (91.4) \| 210 (92.5) \| \| ≤5 days between reported symptom onset and specimen collection \| 23 (74.2) \| 8 (100.0) \| 1 (50.0) \| 120 (71.0) \| 152 (72.4)** \| \* Includes 57 participants who received multiple tests and were included more than once in the analysis. † True positive = antigen-positive and real-time RT-PCR–positive; false negative = antigen-negative and real-time RT-PCR–positive; false positive = antigen-positive and real-time RT-PCR–negative; true negative = antigen-negative and real-time RT-PCR–negative; these definitions do not reflect results from viral culture. § At university A, real-time RT-PCR was performed using the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2. ¶ At university B, real-time RT-PCR was performed using Thermo Fisher Scientific’s TaqPath COVID-19 Combo Kit for detection of SARS-CoV-2. \\ One university staff member’s child aged 15 years. All other participants were aged ≥17 years. †† Non-Hispanic ethnicity represented for all White, Black/African-American, Asian/Pacific Islander, American Indian/Alaska Native, Other/Unknown/Multiple races. §§ Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members. ¶¶ Ever in close contact was defined as within 6 feet for ≥15 minutes of a person with a diagnosis of COVID-19. \\\* Other reported symptoms included allergies, cough that is not dry, and difficulty breathing from anxiety. [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) \| Antigen test result \| Real-time RT-PCR result, no. \| \| \| \| \| \| \|---\|---\|---\|---\|---\|---\|---\| \| Asymptomatic (N = 871) \| Symptomatic\* (N = 227) \| \| \| \| \| \| \| Positive \| Negative \| Total \| Positive \| Negative \| Total \| \| \| Positive \| 7 \| 14 \| **21 \| 32 \| 2 \| 34 \| \| Negative \| 10 \| 840 \| 850 \| 8 \| 185 \| 193 \| \| Total \| 17 \| 854 \| 871 \| 40 \| 187 \| 227 \| \| Test evaluation, % (95% CI) \| \| \| \| \| \| \| \| Sensitivity \| 41\.2 (18.4–67.1) \| 80\.0 (64.4–90.9) \| \| \| \| \| \| Specificity \| 98\.4 (97.3–99.1) \| 98\.9 (96.2–99.9) \| \| \| \| \| \| Positive predictive value \| 33\.3 (14.6–57.0) \| 94\.1 (80.3–99.3) \| \| \| \| \| \| Negative predictive value \| 98\.8 (97.8–99.4) \| 95\.9 (92.0–98.2) \| \| \| \| \| Abbreviation:** CI = confidence interval. \* One or more symptoms reported. [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) ##### [![Return to your place in the text](https://www.cdc.gov/images/arrow_up.gif)](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#F1_up)FIGURE. *Viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) results (n = 69),\ by cycle threshold (Ct) value† and the interval between specimen collection and reported symptom onset or asymptomatic status — university A, Wisconsin, September–October 2020** ![The figure is a scatterplot showing viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction results (n = 69), by cycle threshold value and the interval between specimen collection and reported symptom onset or asymptomatic status at university A in Wisconsin during September–October 2020.](https://www.cdc.gov/mmwr/volumes/69/wr/figures/mm695152a3-F.gif?_=47024) \* n = 30 antigen- and culture-positive; n = 22 antigen-positive and culture-negative; n = 15 antigen- and culture-negative; n = two antigen- negative and culture-positive. † Ct values represent cycle thresholds for the N1 target probe during SARS-CoV-2 real-time RT-PCR; Ct values are represented on the y-axis in descending order to indicate that lower Ct values represent higher levels of RNA in the specimen. [Top](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm) Suggested citation for this article: Pray IW, Ford L, Cole D, et al. Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020. MMWR Morb Mortal Wkly Rep 2021;69:1642–1647. DOI: <http://dx.doi.org/10.15585/mmwr.mm695152a3>. MMWR and Morbidity and Mortality Weekly Report are service marks of the U.S. Department of Health and Human Services. Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services. References to non-CDC sites on the Internet are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. 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Readable Markdown	## Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020 Weekly / January 1, 2021 / 69(5152);1642–1647 *Please note: This report has been corrected.* Ian W. Pray, PhD1,2,3,\; Laura Ford, PhD1,2,\; Devlin Cole, MD3,4; Christine Lee, PhD1,5; John Paul Bigouette, PhD1,2; Glen R. Abedi, MPH1; Dena Bushman, MSN, MPH1,2; Miranda J. Delahoy, PhD1,2; Dustin Currie, PhD1,2; Blake Cherney, MS1; Marie Kirby, PhD1; Geroncio Fajardo, MD1; Motria Caudill, PhD1,6; Kimberly Langolf, MS7; Juliana Kahrs, MS7; Patrick Kelly, MD4,8; Collin Pitts, MD4,8; Ailam Lim, PhD9; Nicole Aulik, PhD9; Azaibi Tamin, PhD1; Jennifer L. Harcourt, PhD1; Krista Queen, PhD1; Jing Zhang, PhD1; Brett Whitaker, PhD1; Hannah Browne1; Magdalena Medrzycki, PhD1; Patricia Shewmaker, PhD1; Jennifer Folster, PhD1; Bettina Bankamp, PhD1; Michael D. Bowen, PhD1; Natalie J. Thornburg, PhD1; Kimberly Goffard, MBA10; Brandi Limbago, PhD1; Allen Bateman, PhD7,11; Jacqueline E. Tate, PhD1; Douglas Gieryn10; Hannah L. Kirking, MD1; Ryan Westergaard, MD, PhD3,4; Marie Killerby, VetMB1; CDC COVID-19 Surge Laboratory Group ([View author affiliations](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#contribAff)) [View suggested citation](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#suggestedcitation) ### Summary What is already known about this topic? Antigen tests for SARS-CoV-2 are inexpensive and can return results within 15 minutes, but test performance data in asymptomatic and symptomatic persons are limited. What is added by this report? Compared with real-time reverse transcription–polymerase chain reaction (RT-PCR) testing, the Sofia antigen test had a sensitivity of 80.0% and specificity of 98.9% among symptomatic persons; accuracy was lower (sensitivity 41.2% and specificity 98.4%) when used for screening of asymptomatic persons. What are the implications for public health practice? To account for reduced antigen test accuracy, confirmatory testing with a nucleic acid amplification test (e.g., RT-PCR) should be considered after negative antigen test results in symptomatic persons and positive antigen test results in asymptomatic persons. ##### Altmetric: Mendeley (295) ## Discussion The Sofia SARS Antigen FIA received FDA EUA on May 8, 2020, for use in symptomatic persons within 5 days of symptom onset (2). In this investigation, among persons reporting COVID-19–compatible symptoms at specimen collection, the test was less accurate (sensitivity = 80.0%; specificity = 98.9%) than reported in the FDA EUA (sensitivity = 96.7%; specificity = 100%) (2). Two of eight specimens from symptomatic persons that had false-negative antigen test results were positive by viral culture, indicating that potentially infectious persons might not be detected by antigen testing. To reduce the impact of false-negative antigen test results, confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, should be considered following negative antigen test results in symptomatic persons (1). Among asymptomatic participants, antigen test sensitivity was 41.2%, specificity was 98.4%, and PPV in this population was 33.3%. This low PPV was observed despite a relatively high prevalence of SARS-CoV-2 in this population (5.2% prevalence overall; 2.0% among asymptomatic persons), suggesting that PPV could be even lower when using this antigen test among populations with lower expected SARS-CoV-2 prevalence. To account for false-positive results when using antigen tests for asymptomatic screening, confirmatory NAAT testing should be considered following positive antigen test results in asymptomatic persons, particularly when pretest probability of SARS-CoV-2 infection is low (1). The NPV of antigen testing among asymptomatic participants was 98.8%, and virus was not cultured from asymptomatic participants with antigen-negative results, indicating that asymptomatic persons with negative antigen results are unlikely to be infected with SARS-CoV-2 and would not require confirmatory NAAT (1). The findings in this report are subject to at least four limitations. First, participants were predominantly young adults in university settings where ongoing serial testing was being conducted. Antigen test performance might differ in other populations with different characteristics and testing schedules. Second, given the limitations of RT-PCR, some false-positive antigen test results might represent true infections not identified by RT-PCR. Third, the ability to recover infectious virus in culture is limited and decreases for specimens with higher Ct values (8); a lack of virus recovery by culture does not indicate that a person is not infectious. Finally, this investigation evaluated the Sofia SARS Antigen FIA, and cannot be generalized to other FDA-authorized SARS-CoV-2 antigen tests. Serial testing of asymptomatic and symptomatic persons has been proposed for prevention and control of SARS-CoV-2 transmission (9,10) and is currently being implemented at U.S. colleges and universities and in other congregate settings (3–5). Despite reduced sensitivity compared with real-time RT-PCR, the use of antigen tests for serial testing in these settings, particularly when RT-PCR tests are not available or have a prolonged turnaround time, might still allow rapid identification of infectious persons and control of outbreaks (1). However, antigen-based testing strategies should account for the lower sensitivity and lower PPV when used for asymptomatic screening by considering confirmatory testing with an FDA-authorized NAAT, such as RT-PCR, after a positive antigen test result in an asymptomatic person. Confirmatory testing should also be considered following a negative antigen test result in a person experiencing COVID-19–compatible symptoms. All persons with negative antigen test results should continue to take measures to prevent SARS-CoV-2 transmission, including wearing a mask, reducing contact with nonhousehold members, and getting tested if they experience symptoms or have close contact with someone who has COVID-19.††† Symptomatic persons with negative antigen test results should continue to follow CDC guidance§§§ for persons who might have COVID-19, including staying home except to get medical care and protecting household members by staying in a separate room, wearing a mask indoors, washing hands often, and frequently disinfecting surfaces. ### Acknowledgments Edward Samuel Rivera, Daniel J. O’Donnell, University of Wisconsin-Oshkosh; Margaret Okomo-Adhiambo, Umesh Parashar, Paul Rota, Lauren Franco, Gerardo Garcia-Lerma, CDC; Neeti Dahal, Wisconsin Veterinary Diagnostic Laboratory-Wisconsin State Laboratory of Hygiene COVID Laboratory, University of Wisconsin-Madison. ### CDC COVID-19 Surge Laboratory Group Baoming Jiang, CDC; Jan Vinjé, CDC; Amy L. Hopkins, CDC; Eric Katz, CDC; Leslie Barclay, CDC; Mathew Esona, CDC; Rashi Gautam, CDC; Slavica Mijatovic-Rustempasic, CDC; Sung-Sil Moon, CDC; Theresa Bessey, CDC; Preeti Chhabra, CDC; Sarah L. Smart, CDC; Raydel Anderson, CDC; Kay W. Radford, CDC; Gimin Kim, CDC; Dexter Thompson, CDC; Congrong Miao, CDC; Min-hsin Chen, CDC; Lalitha Gade, CDC; Renee Galloway, CDC; Kashif Sahibzada, CDC; Nhien M. Tran, CDC; Srinivasan Velusamy, CDC; HaoQiang Zheng, CDC; Kenny Nguyen, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Claire Hartloge, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Brent Jenkins, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee; Phili Wong, Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee *** 1CDC COVID-19 Response Team; 2Epidemic Intelligence Service, CDC; 3Wisconsin Department of Health Services; 4School of Medicine and Public Health, University of Wisconsin-Madison; 5Laboratory Leadership Service, CDC; 6Agency for Toxic Substances and Disease Registry, Atlanta, Georgia; 7University of Wisconsin-Oshkosh; 8University Health Services, University of Wisconsin-Madison; 9Wisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison; 10Winnebago County Health Department, Oshkosh, Wisconsin; 11Wisconsin State Laboratory of Hygiene. All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed. \* These authors contributed equally to this report. † Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members. § Symptom list was based on the interim position statement for COVID-19 case definitions from the Council of State and Territorial Epidemiologists, updated August 7, 2020. Clinical criteria for COVID-19 included fever, cough, shortness of breath, fatigue, sore throat, headache, muscle aches, chills, nasal congestion, difficulty breathing, diarrhea, nausea, vomiting, abdominal pain, rigors, loss of taste, and loss of smell. <https://cdn.ymaws.com/www.cste.org/resource/resmgr/ps/positionstatement2020/Interim-20-ID-02_COVID-19.pdf>. ¶ Recent exposure was defined as being within 6 feet of a person with a COVID-19 diagnosis for ≥15 minutes in the past 14 days. \\ <https://www.fda.gov/media/137885/download>. †† Specimens were used to perform a limiting-dilution inoculation of Vero CCL-81 cells, and cultures showing evidence of cytopathic effect (CPE) were tested by real-time RT-PCR for the presence of SARS-CoV-2 RNA. Viral recovery was defined as any culture in which the first passage had an N1 Ct at least twofold lower than the corresponding clinical specimen. §§ Ct values from real-time RT-PCR were only compared for specimens collected at university A that were analyzed with the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2. ¶¶ 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect. 552a; 44 U.S.C. Sect. 3501 et seq. \\\* The participant with a false-negative result 2 days after symptom onset had a repeat specimen 2 days later; the results of testing were positive by antigen test and by real-time RT-PCR. ††† <https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html>. §§§ <https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/steps-when-sick.html>. ## References 1. CDC. Coronavirus disease 2019 (COVID-19): interim guidance for antigen testing for SARS-CoV-2. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antigen-tests-guidelines.html> 2. Food and Drug Administration. In vitro diagnostics EUAs. Silver Spring, MD: US Department of Health and Human Services, Food and Drug Administration; 2020. <https://www.fda.gov/medical-devices/coronavirus-disease-2019-covid-19-emergency-use-authorizations-medical-devices/vitro-diagnostics-euas> 3. CDC. Coronavirus disease 2019 (COVID-19): guidance for testing, screening, and outbreak response for institutions of higher education (IHEs). Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/community/colleges-universities/ihe-testing.html> 4. CDC. Coronavirus disease 2019 (COVID-19): testing guidelines for nursing homes. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/hcp/nursing-homes-testing.html> 5. CDC. Coronavirus disease 2019 (COVID-19): interim considerations for SARS-CoV-2 testing in correctional and detention facilities. Atlanta, GA: US Department of Health and Human Services, CDC; 2020. <https://www.cdc.gov/coronavirus/2019-ncov/community/correction-detention/testing.html> 6. Lu X, Wang L, Sakthivel SK, et al. US CDC real-time reverse transcription PCR panel for detection of severe acute respiratory syndrome coronavirus 2. Emerg Infect Dis 2020;26:1654–65. [CrossRef](http://dx.doi.org/10.3201/eid2608.201246) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/32396505) 7. Harcourt J, Tamin A, Lu X, et al. Severe acute respiratory syndrome coronavirus 2 from patient with coronavirus disease, United States. Emerg Infect Dis 2020;26:1266–73. [CrossRef](http://dx.doi.org/10.3201/eid2606.200516) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/32160149) 8. Gniazdowski V, Morris CP, Wohl S, et al. 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[CrossRef](http://dx.doi.org/10.1001/jamanetworkopen.2020.16818) [PubMed](http://www.ncbi.nlm.nih.gov/pubmed/32735339) \| Characteristic \| No (%) \| \| \| \| \| \|---\|---\|---\|---\|---\|---\| \| True positives (N = 39) \| False negatives (N = 18) \| False positives (N = 16) \| True negatives (N = 1,025) \| Total (N = 1,098) \| \| \| **Testing site \| \| \| \| \| \| \| University A§ \| 37 (94.9) \| 17 (94.4) \| 15 (93.8) \| 982 (95.8) \| 1,051 (95.7) \| \| University B¶ \| 2 (5.1) \| 1 (5.6) \| 1 (6.3) \| 43 (4.2) \| 47 (4.3) \| \| Sex \| \| \| \| \| \| \| Male \| 16 (41.0) \| 9 (50.0) \| 12 (75.0) \| 416 (40.6) \| 453 (41.3) \| \| Female \| 23 (59.0) \| 9 (50.0) \| 4 (25.0) \| 609 (59.4) \| 645 (58.7) \| \| Age group (yrs)** \| \| \| \| \| \| \| 15–24\\ \| 35 (89.7) \| 16 (88.9) \| 11 (68.8) \| 909 (88.7) \| **971 (88.4) \| \| ≥25 \| 4 (10.3) \| 2 (11.1) \| 5 (31.3) \| 116 (11.3) \| 127 (11.6) \| \| Race/Ethnicity†† \| \| \| \| \| \| \| White \| 31 (79.5) \| 17 (94.4) \| 12 (75.0) \| 857 (83.6) \| 917 (83.5) \| \| Hispanic/Latino \| 6 (15.4) \| 0 (0) \| 1 (6.3) \| 54 (5.3) \| 61 (5.6) \| \| Black/African-American \| 0 (0) \| 1 (5.6) \| 2 (12.5) \| 26 (2.5) \| 29 (2.6) \| \| Asian/Pacific Islander \| 0 (0) \| 0 (0) \| 0 (0) \| 49 (4.8) \| 49 (4.5) \| \| American Indian/Alaska Native \| 0 (0) \| 0 (0) \| 0 (0) \| 3 (0.3) \| 3 (0.3) \| \| Other/Unknown/Multiple races \| 2 (5.1) \| 0 (0) \| 1 (6.3) \| 36 (3.5) \| 39 (3.6) \| \| University status \| \| \| \| \| \| \| Student \| 35 (89.7) \| 17 (94.4) \| 13 (81.3) \| 929 (90.6) \| 994 (90.5) \| \| Faculty or staff member \| 4 (10.3) \| 1 (5.6) \| 3 (18.8) \| 74 (7.2) \| 82 (7.5) \| \| Other affiliate or unknown§§ \| 0 (0) \| 0 (0) \| 0 (0) \| 22 (2.2) \| 22 (2.0) \| \| Exposure¶¶ to a COVID-19 case \| \| \| \| \| \| \| Been in close contact in the past 14 days \| 13 (33.3) \| 9 (50.0) \| 4 (25.0) \| 128 (12.5) \| 154 (14.0) \| \| Quarantine status \| \| \| \| \| \| \| Quarantined at time of specimen collection \| 17 (43.6) \| 6 (33.3) \| 3 (18.8) \| 109 (10.6) \| 135 (12.3) \| \| Time between quarantine initiation to specimen collection, median days (range) \| 1 (0–8) \| 3\.5 (0–6) \| 1 (0–4) \| 4 (0–28) \| 4 (0–28) \| \| Reported symptoms \| \| \| \| \| \| \| No current symptoms \| 7 (17.9) \| 10 (55.6) \| 14 (87.5) \| 840 (82.0) \| 871 (79.3) \| \| One or more symptoms in the past 14 days \| 2 (28.6) \| 1 (10.0) \| 0 (0) \| 50 (6.0) \| 53 (6.1) \| \| No symptoms in the past 14 days \| 5 (71.4) \| 9 (90.0) \| 14 (100.0) \| 790 (94.0) \| 818 (93.9) \| \| One or more current symptoms \| 32 (82.1) \| 8 (44.4) \| 2 (12.5) \| 185 (18.0) \| 227 (20.7) \| \| Nasal congestion \| 24 (75.0) \| 2 (25.0) \| 1 (50.0) \| 87 (47.0) \| 114 (50.2) \| \| Sore throat \| 12 (37.5) \| 5 (62.5) \| 1 (50.0) \| 79 (42.7) \| 97 (42.7) \| \| Headache \| 17 (53.1) \| 3 (37.5) \| 1 (50.0) \| 66 (35.7) \| 87 (38.3) \| \| Cough \| 18 (56.3) \| 6 (75.0) \| 1 (50.0) \| 45 (24.3) \| 70 (30.8) \| \| Fatigue \| 14 (43.8) \| 3 (37.5) \| 1 (50.0) \| 42 (22.7) \| 60 (26.4) \| \| Muscle aches \| 11 (34.4) \| 2 (25.0) \| 0 (0) \| 30 (16.2) \| 43 (18.9) \| \| Shortness of breath \| 7 (21.9) \| 1 (12.5) \| 0 (0) \| 16 (8.6) \| 24 (10.6) \| \| Chills \| 4 (12.5) \| 0 (0) \| 0 (0) \| 14 (7.6) \| 18 (7.9) \| \| Diarrhea \| 3 (9.4) \| 0 (0) \| 0 (0) \| 15 (8.1) \| 18 (7.9) \| \| Nausea or vomiting \| 3 (9.4) \| 0 (0) \| 0 (0) \| 14 (7.6) \| 17 (7.5) \| \| Loss of taste \| 8 (25.0) \| 2 (25.0) \| 1 (50.0) \| 3 (1.6) \| 14 (6.2) \| \| Loss of smell \| 8 (25.0) \| 2 (25.0) \| 1 (50.0) \| 2 (1.1) \| 13 (5.7) \| \| Fever \| 6 (18.8) \| 0 (0) \| 0 (0) \| 5 (2.7) \| 11 (4.8) \| \| Difficulty breathing \| 3 (9.4) \| 0 (0) \| 0 (0) \| 8 (4.3) \| 11 (4.8) \| \| Abdominal pain \| 1 (3.1) \| 0 (0) \| 0 (0) \| 6 (3.2) \| 7 (3.1) \| \| Rigors \| 0 (0) \| 0 (0) \| 0 (0) \| 0 (0) \| 0 (0.0)** \| \| Other reported symptoms\\\* \| 1 (3.1) \| 0 (0) \| 0 (0) \| 4 (2.2) \| **5 (2.2) \| \| Symptom onset date reported \| 31 (96.9) \| 8 (100.0) \| 2 (100.0) \| 169 (91.4) \| 210 (92.5) \| \| ≤5 days between reported symptom onset and specimen collection \| 23 (74.2) \| 8 (100.0) \| 1 (50.0) \| 120 (71.0) \| 152 (72.4)** \| \* Includes 57 participants who received multiple tests and were included more than once in the analysis. † True positive = antigen-positive and real-time RT-PCR–positive; false negative = antigen-negative and real-time RT-PCR–positive; false positive = antigen-positive and real-time RT-PCR–negative; true negative = antigen-negative and real-time RT-PCR–negative; these definitions do not reflect results from viral culture. § At university A, real-time RT-PCR was performed using the CDC 2019-nCoV real-time RT-PCR diagnostic panel for detection of SARS-CoV-2. ¶ At university B, real-time RT-PCR was performed using Thermo Fisher Scientific’s TaqPath COVID-19 Combo Kit for detection of SARS-CoV-2. \\ One university staff member’s child aged 15 years. All other participants were aged ≥17 years. †† Non-Hispanic ethnicity represented for all White, Black/African-American, Asian/Pacific Islander, American Indian/Alaska Native, Other/Unknown/Multiple races. §§ Other affiliates were participants who did not mark “student” or “staff” on the questionnaire (they selected “other” or did not respond); the majority of these persons were family members of staff members. ¶¶ Ever in close contact was defined as within 6 feet for ≥15 minutes of a person with a diagnosis of COVID-19. \\\* Other reported symptoms included allergies, cough that is not dry, and difficulty breathing from anxiety. \| Antigen test result \| Real-time RT-PCR result, no. \| \| \| \| \| \| \|---\|---\|---\|---\|---\|---\|---\| \| Asymptomatic (N = 871) \| Symptomatic\* (N = 227) \| \| \| \| \| \| \| Positive \| Negative \| Total \| Positive \| Negative \| Total \| \| \| Positive \| 7 \| 14 \| **21 \| 32 \| 2 \| 34 \| \| Negative \| 10 \| 840 \| 850 \| 8 \| 185 \| 193 \| \| Total \| 17 \| 854 \| 871 \| 40 \| 187 \| 227 \| \| Test evaluation, % (95% CI) \| \| \| \| \| \| \| \| Sensitivity \| 41\.2 (18.4–67.1) \| 80\.0 (64.4–90.9) \| \| \| \| \| \| Specificity \| 98\.4 (97.3–99.1) \| 98\.9 (96.2–99.9) \| \| \| \| \| \| Positive predictive value \| 33\.3 (14.6–57.0) \| 94\.1 (80.3–99.3) \| \| \| \| \| \| Negative predictive value \| 98\.8 (97.8–99.4) \| 95\.9 (92.0–98.2) \| \| \| \| \| Abbreviation:** CI = confidence interval. \* One or more symptoms reported. ##### [![Return to your place in the text](https://www.cdc.gov/images/arrow_up.gif)](https://www.cdc.gov/mmwr/volumes/69/wr/mm695152a3.htm#F1_up)FIGURE. *Viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction (RT-PCR) results (n = 69),\ by cycle threshold (Ct) value† and the interval between specimen collection and reported symptom onset or asymptomatic status — university A, Wisconsin, September–October 2020** ![The figure is a scatterplot showing viral culture results among participants with positive Sofia SARS Antigen Fluorescent Immunoassay or positive SARS-CoV-2 real-time reverse transcription–polymerase chain reaction results (n = 69), by cycle threshold value and the interval between specimen collection and reported symptom onset or asymptomatic status at university A in Wisconsin during September–October 2020.](https://www.cdc.gov/mmwr/volumes/69/wr/figures/mm695152a3-F.gif?_=47024) \* n = 30 antigen- and culture-positive; n = 22 antigen-positive and culture-negative; n = 15 antigen- and culture-negative; n = two antigen- negative and culture-positive. † Ct values represent cycle thresholds for the N1 target probe during SARS-CoV-2 real-time RT-PCR; Ct values are represented on the y-axis in descending order to indicate that lower Ct values represent higher levels of RNA in the specimen. Suggested citation for this article: Pray IW, Ford L, Cole D, et al. Performance of an Antigen-Based Test for Asymptomatic and Symptomatic SARS-CoV-2 Testing at Two University Campuses — Wisconsin, September–October 2020. MMWR Morb Mortal Wkly Rep 2021;69:1642–1647. DOI: <http://dx.doi.org/10.15585/mmwr.mm695152a3>. MMWR and Morbidity and Mortality Weekly Report are service marks of the U.S. Department of Health and Human Services. Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Department of Health and Human Services. References to non-CDC sites on the Internet are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites. URL addresses listed in MMWR were current as of the date of publication. 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