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Response:

Calculated Shard: 124 (from laksa158)

2. Crawled Status Check

Query:

curl -X POST \
  'http://laksa124.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.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests\')), getAhrefsUnparsedNoserviceFromURL(\'https://www.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests\'))) FORMAT JSONEachRow'

Response:

{"found_url":"https:\/\/www.mcgill.ca\/oss\/article\/covid-19\/navigating-false-negatives-covid-rapid-tests","crawl_time":1775320439,"first_indexed_time":1649185619,"http_code":200,"src_unparsed":"ca,mcgill!www,\/oss\/article\/covid-19\/navigating-false-negatives-covid-rapid-tests s443","src_root_hash":"18239483145122604324","history_drop_reason":null,"meta_title":"Navigating False Negatives on COVID Rapid Tests - McGill University","meta_descriptions":["If you think you have COVID and test negative, you need to test again."],"attrs_boilerpipe_text":"This article was originally posted in the\nMontreal Gazette\n.\nIt should be clear by this point that \nwe are in a sixth wave\n driven by the BA.2 variant. With COVID cases and hospitalizations rising, it still remains somewhat unclear how high they will go and how long it will last. But what is stymying many people this time around and making the whole issue more complicated is the issue of testing.\nAfter the fifth wave, widespread PCR testing stopped because the system simply couldn’t cope. Rapid tests became, out of necessity, the standard testing strategy for the general population. There are obviously several advantages to rapid tests. They are cheaper, more widely available, can be done at home and do not require medical personnel to administer them.\nBut, there is the issue of test accuracy. False positives with rapid tests are extremely rare, with one research letter in \nJAMA\n pegging the false positivity rate at 0.05% and many of these false positives were traced back to a single batch of tests, which suggests it was a specific quality control issue rather than a question of decreased test accuracy.\nBut while false positives are rare, false negatives are not. It seems, from anecdotal experience, that we are seeing more false negatives during this wave, which has led to speculation that the tests may not perform as well against the Omicron variant and now BA.2. (The new variant has not been around long enough to generate enough data, but the assumption is that it would behave the same way as Omicron, given their similarity.)\nThere is a theoretical basis for this concern. The Omicron variant in particular had mutations on the S-gene that coded for the spike protein and might not be detected by some laboratory tests. The U.S. Food and Drug Administration keeps an ongoing \nlist\n of specific test kits that may have issues with new variants, but don’t specifically mention any rapid tests that have issues with the Omicron variant. The FDA does say, “early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” but does not raise any specific issues or provide any data.\nThe Ontario Science Table did \nreview\n the sensitivity of rapid tests against the Delta and Omicron variants and found, in unpublished studies, that the sensitivity against Omicron was clearly lower than it was for Delta. Its analysis suggested that the sensitivity of rapid tests to detect the Omicron variant was 37 percent, compared to 81 percent for Delta. In effect, this means that if 100 people had COVID and were infected with the Omicron variant, only 37 of them would get a positive result and the others would get a falsely negative result.\nOn the surface, this would seem concerning and would likely explain why many people have reported testing negative at first only to then be diagnosed with COVID-19 a few days later. But, it’s important to point out the test sensitivity does vary between studies and another unpublished \nstudy\n not included in that review found that the sensitivity of the tests with respect to Omicron ranged between 65 and 95 percent in the different patient populations. Also, while test sensitivity was low overall, it was over 80 percent after Day 3 of the infection and improved considerably with repeat testing.\nWhether the genetic changes in new variants are having an impact on test accuracy is not entirely clear. Part of the problem is that the predictive value of test changes as disease prevalence changes. As diseases become more common, the relative number of true positives vs. false positives shifts and we get fewer false positives but consequently more false negatives. So as COVID cases surge, we must expect more false negatives, for purely mathematical reasons.\nThe solution, though, is clear. If you think you have COVID and test negative, you need to test again.\n@DrLabos","attrs_markdown":"[McGill University](https:\/\/www.mcgill.ca\/ \"return to McGill University\")\n\n[Office for Science and Society](https:\/\/www.mcgill.ca\/oss\/)\n\nSeparating Sense from Nonsense\n\n## Main navigation\n- [Home](https:\/\/www.mcgill.ca\/oss\/)\n- [Our Articles](https:\/\/www.mcgill.ca\/oss\/our-articles)\n- [Who We Are](https:\/\/www.mcgill.ca\/oss\/people)\n- [Dr. Joe's Books](https:\/\/www.mcgill.ca\/oss\/books)\n- [Events](https:\/\/www.mcgill.ca\/oss\/events)\n- [Our History](https:\/\/www.mcgill.ca\/oss\/our-history)\n- [Public Lectures](https:\/\/www.mcgill.ca\/oss\/publiclectures)\n- [Past Newsletters](https:\/\/www.mcgill.ca\/oss\/past-newsletters)\n- [Contributor Submission](https:\/\/www.mcgill.ca\/oss\/contributor-submission)\n- [Photo Gallery: The McGill OSS Separates 25 Years of Separating Sense from Nonsense](https:\/\/www.mcgill.ca\/oss\/photo-gallery-mcgill-oss-separates-25-years-separating-sense-nonsense \"Photo Gallery: The McGill OSS Separates 25 Years of Separating Sense from Nonsense\")\n\n## Subscribe to the OSS Weekly Newsletter\\!\n[Sign-Up Here](https:\/\/e1.envoke.com\/ext\/pages\/4244cddff96d640b64864b5906677412)\n\n[Home](https:\/\/www.mcgill.ca\/oss\/)\n\n# Navigating False Negatives on COVID Rapid Tests\nIf you think you have COVID and test negative, you need to test again.\n\n![](https:\/\/www.mcgill.ca\/oss\/files\/oss\/styles\/hd\/public\/test-g8be875e96_1920.jpeg?itok=YUvCrveb&timestamp=1649185364)\n\n[Christopher Labos MD, MSc](https:\/\/www.mcgill.ca\/oss\/articles-by-author\/Christopher%20Labos%20MD,%20MSc) \\| 5 Apr 2022\n\n[COVID-19](https:\/\/www.mcgill.ca\/oss\/category\/article-categories\/covid-19)\n\n- [Add to calendar](https:\/\/www.mcgill.ca\/oss\/node\/9073\/ical \"Add to calendar\")\n- [Facebook](http:\/\/www.facebook.com\/sharer.php?u=https%3A\/\/www.mcgill.ca\/oss\/article\/covid-19\/navigating-false-negatives-covid-rapid-tests&t=Navigating%20False%20Negatives%20on%20COVID%20Rapid%20Tests \"Share on Facebook\")\n- [LinkedIn](http:\/\/www.linkedin.com\/shareArticle?mini=true&url=https%3A\/\/www.mcgill.ca\/oss\/article\/covid-19\/navigating-false-negatives-covid-rapid-tests&title=Navigating%20False%20Negatives%20on%20COVID%20Rapid%20Tests&summary=%0D%0AThis%20article%20was%20originally%20posted%20in%20the%20Montreal%20Gazette.&source=Office%20for%20Science%20and%20Society%20 \"Publish this post to LinkedIn\")\n- [Tweet Widget](http:\/\/twitter.com\/share?url=https%3A\/\/www.mcgill.ca\/oss\/article\/covid-19\/navigating-false-negatives-covid-rapid-tests&count=horizontal&via=McGillOSS&text=Navigating%20False%20Negatives%20on%20COVID%20Rapid%20Tests&counturl=https%3A\/\/www.mcgill.ca\/oss\/article\/covid-19\/navigating-false-negatives-covid-rapid-tests \"Tweet This\")\n\n***\n*This article was originally posted in the [Montreal Gazette](https:\/\/montrealgazette.com\/opinion\/columnists\/christopher-labos-navigating-false-negatives-on-covid-rapid-tests).*\n***\nIt should be clear by this point that [we are in a sixth wave](https:\/\/montrealgazette.com\/news\/local-news\/quebec-now-officially-in-pandemics-sixth-wave-inspq-says) driven by the BA.2 variant. With COVID cases and hospitalizations rising, it still remains somewhat unclear how high they will go and how long it will last. But what is stymying many people this time around and making the whole issue more complicated is the issue of testing.\n\nAfter the fifth wave, widespread PCR testing stopped because the system simply couldn’t cope. Rapid tests became, out of necessity, the standard testing strategy for the general population. There are obviously several advantages to rapid tests. They are cheaper, more widely available, can be done at home and do not require medical personnel to administer them.\n\nBut, there is the issue of test accuracy. False positives with rapid tests are extremely rare, with one research letter in [JAMA](https:\/\/jamanetwork.com\/journals\/jama\/fullarticle\/2788067) pegging the false positivity rate at 0.05% and many of these false positives were traced back to a single batch of tests, which suggests it was a specific quality control issue rather than a question of decreased test accuracy.\n\nBut while false positives are rare, false negatives are not. It seems, from anecdotal experience, that we are seeing more false negatives during this wave, which has led to speculation that the tests may not perform as well against the Omicron variant and now BA.2. (The new variant has not been around long enough to generate enough data, but the assumption is that it would behave the same way as Omicron, given their similarity.)\n\nThere is a theoretical basis for this concern. The Omicron variant in particular had mutations on the S-gene that coded for the spike protein and might not be detected by some laboratory tests. The U.S. Food and Drug Administration keeps an ongoing [list](https:\/\/www.fda.gov\/medical-devices\/coronavirus-covid-19-and-medical-devices\/sars-cov-2-viral-mutations-impact-covid-19-tests#omicronbackground) of specific test kits that may have issues with new variants, but don’t specifically mention any rapid tests that have issues with the Omicron variant. The FDA does say, “early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” but does not raise any specific issues or provide any data.\n\nThe Ontario Science Table did [review](https:\/\/covid19-sciencetable.ca\/sciencebrief\/use-of-rapid-antigen-tests-during-the-omicron-wave\/) the sensitivity of rapid tests against the Delta and Omicron variants and found, in unpublished studies, that the sensitivity against Omicron was clearly lower than it was for Delta. Its analysis suggested that the sensitivity of rapid tests to detect the Omicron variant was 37 percent, compared to 81 percent for Delta. In effect, this means that if 100 people had COVID and were infected with the Omicron variant, only 37 of them would get a positive result and the others would get a falsely negative result.\n\nOn the surface, this would seem concerning and would likely explain why many people have reported testing negative at first only to then be diagnosed with COVID-19 a few days later. But, it’s important to point out the test sensitivity does vary between studies and another unpublished [study](https:\/\/www.medrxiv.org\/content\/10.1101\/2022.01.08.22268954v2.full) not included in that review found that the sensitivity of the tests with respect to Omicron ranged between 65 and 95 percent in the different patient populations. Also, while test sensitivity was low overall, it was over 80 percent after Day 3 of the infection and improved considerably with repeat testing.\n\nWhether the genetic changes in new variants are having an impact on test accuracy is not entirely clear. Part of the problem is that the predictive value of test changes as disease prevalence changes. As diseases become more common, the relative number of true positives vs. false positives shifts and we get fewer false positives but consequently more false negatives. So as COVID cases surge, we must expect more false negatives, for purely mathematical reasons.\n\nThe solution, though, is clear. If you think you have COVID and test negative, you need to test again.\n***\n[@DrLabos](http:\/\/twitter.com\/drlabos)\n\nKeywords:\n\n[rapid test](https:\/\/www.mcgill.ca\/oss\/category\/tags\/rapid-test)\n\n[antigen test](https:\/\/www.mcgill.ca\/oss\/category\/tags\/antigen-test)\n\n[false negative](https:\/\/www.mcgill.ca\/oss\/category\/tags\/false-negative)\n\n[false positive](https:\/\/www.mcgill.ca\/oss\/category\/tags\/false-positive)\n\n[Covid](https:\/\/www.mcgill.ca\/oss\/category\/tags\/covid)\n\n[sixth wave](https:\/\/www.mcgill.ca\/oss\/category\/tags\/sixth-wave)\n\n[Omicron variant](https:\/\/www.mcgill.ca\/oss\/category\/tags\/omicron-variant)\n\n[BA.2](https:\/\/www.mcgill.ca\/oss\/category\/tags\/ba2)\n\n## What to read next\n## [TZLA Plasma Healing: The Anarcho-Capitalist Cure-All 26 Mar 2026](https:\/\/www.mcgill.ca\/oss\/article\/covid-19-medical-critical-thinking-pseudoscience\/tzla-plasma-healing-anarcho-capitalist-cure-all \" TZLA Plasma Healing: The Anarcho-Capitalist Cure-All\")\n![](https:\/\/www.mcgill.ca\/oss\/files\/oss\/styles\/large\/public\/banner_for_tzla_v2.png?itok=hMci-7BU)\n\n## [Rare Blood Clots After Certain COVID Vaccines, Explained 19 Feb 2026](https:\/\/www.mcgill.ca\/oss\/article\/covid-19-medical-health-and-nutrition-technology\/rare-blood-clots-after-certain-covid-vaccines-explained \"Rare Blood Clots After Certain COVID Vaccines, Explained\")\n![](https:\/\/www.mcgill.ca\/oss\/files\/oss\/styles\/large\/public\/banner_for_covid_vaccine_blood_clots_v1.png?itok=ZIoP4W7c)\n\n## [The Strange Story of Nicotine Patches to Treat Long COVID 20 Nov 2025](https:\/\/www.mcgill.ca\/oss\/article\/medical-health-and-nutrition-pseudoscience\/strange-story-nicotine-patches-treat-long-covid \"The Strange Story of Nicotine Patches to Treat Long COVID\")\n![](https:\/\/www.mcgill.ca\/oss\/files\/oss\/styles\/large\/public\/banner_for_nicotine_v1.jpg?itok=P6K1pR2j)\n\n## [Everyone Else Is Lying to You: A Damning Archive of Science Denial 16 Oct 2025](https:\/\/www.mcgill.ca\/oss\/article\/pseudoscience-reviews\/everyone-else-lying-you-damning-archive-science-denial \"Everyone Else Is Lying to You: A Damning Archive of Science Denial\")\n![](https:\/\/www.mcgill.ca\/oss\/files\/oss\/styles\/large\/public\/banner_for_everyone_else_is_lying_to_you_v1.jpg?itok=TJRsDZ7-)\n\n## [How We Know that Vaccines Are Safe 21 Feb 2025](https:\/\/www.mcgill.ca\/oss\/article\/covid-19-medical-critical-thinking\/how-we-know-vaccines-are-safe \"How We Know that Vaccines Are Safe\")\n![](https:\/\/www.mcgill.ca\/oss\/files\/oss\/styles\/large\/public\/vax.png?itok=AZKsB4Bv)\n\n## [Bret Weinstein, Would-Be Galileo 27 Sep 2024](https:\/\/www.mcgill.ca\/oss\/article\/covid-19-critical-thinking\/bret-weinstein-would-be-galileo \"Bret Weinstein, Would-Be Galileo\")\n![](https:\/\/www.mcgill.ca\/oss\/files\/oss\/styles\/large\/public\/weinstein_banner_image_v1.jpg?itok=EDFuF-ZO)\n\n[Back to top](https:\/\/www.mcgill.ca\/oss\/article\/covid-19\/navigating-false-negatives-covid-rapid-tests)\n\n## Department and University Information\n## Office for Science and Society\nMcGill University  \n 801 Sherbrooke Street West  \n Montreal, Quebec H3A 0B8\n\n![Office for Science and Society ](https:\/\/www.mcgill.ca\/oss\/files\/oss\/moriarty_branding_img.jpg)\n\n[Facebook](https:\/\/www.facebook.com\/McGillOSS \"Follow us on Facebook\") [YouTube](http:\/\/www.youtube.com\/mcgilloss \"Follow us on YouTube\") [Instagram](https:\/\/www.instagram.com\/mcgilloss\/ \"Follow us on Instagram\") [Bluesky](https:\/\/bsky.app\/profile\/mcgilloss.bsky.social \"Follow us on Bluesky\")\n\n[McGill University](https:\/\/www.mcgill.ca\/ \"return to McGill University\")\n\nCopyright © 2026 McGill University\n\n[Accessibility](https:\/\/www.mcgill.ca\/accessibility \"Accessibility\") [Cookie notice](https:\/\/www.mcgill.ca\/cookie-notice \"Cookie notice\")\n\nCookie settings\n\n[Log in](https:\/\/www.mcgill.ca\/oss\/saml_login?destination=node\/9073)","attrs_readable_markdown":"***\n*This article was originally posted in the [Montreal Gazette](https:\/\/montrealgazette.com\/opinion\/columnists\/christopher-labos-navigating-false-negatives-on-covid-rapid-tests).*\n***\nIt should be clear by this point that [we are in a sixth wave](https:\/\/montrealgazette.com\/news\/local-news\/quebec-now-officially-in-pandemics-sixth-wave-inspq-says) driven by the BA.2 variant. With COVID cases and hospitalizations rising, it still remains somewhat unclear how high they will go and how long it will last. But what is stymying many people this time around and making the whole issue more complicated is the issue of testing.\n\nAfter the fifth wave, widespread PCR testing stopped because the system simply couldn’t cope. Rapid tests became, out of necessity, the standard testing strategy for the general population. There are obviously several advantages to rapid tests. They are cheaper, more widely available, can be done at home and do not require medical personnel to administer them.\n\nBut, there is the issue of test accuracy. False positives with rapid tests are extremely rare, with one research letter in [JAMA](https:\/\/jamanetwork.com\/journals\/jama\/fullarticle\/2788067) pegging the false positivity rate at 0.05% and many of these false positives were traced back to a single batch of tests, which suggests it was a specific quality control issue rather than a question of decreased test accuracy.\n\nBut while false positives are rare, false negatives are not. It seems, from anecdotal experience, that we are seeing more false negatives during this wave, which has led to speculation that the tests may not perform as well against the Omicron variant and now BA.2. (The new variant has not been around long enough to generate enough data, but the assumption is that it would behave the same way as Omicron, given their similarity.)\n\nThere is a theoretical basis for this concern. The Omicron variant in particular had mutations on the S-gene that coded for the spike protein and might not be detected by some laboratory tests. The U.S. Food and Drug Administration keeps an ongoing [list](https:\/\/www.fda.gov\/medical-devices\/coronavirus-covid-19-and-medical-devices\/sars-cov-2-viral-mutations-impact-covid-19-tests#omicronbackground) of specific test kits that may have issues with new variants, but don’t specifically mention any rapid tests that have issues with the Omicron variant. The FDA does say, “early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” but does not raise any specific issues or provide any data.\n\nThe Ontario Science Table did [review](https:\/\/covid19-sciencetable.ca\/sciencebrief\/use-of-rapid-antigen-tests-during-the-omicron-wave\/) the sensitivity of rapid tests against the Delta and Omicron variants and found, in unpublished studies, that the sensitivity against Omicron was clearly lower than it was for Delta. Its analysis suggested that the sensitivity of rapid tests to detect the Omicron variant was 37 percent, compared to 81 percent for Delta. In effect, this means that if 100 people had COVID and were infected with the Omicron variant, only 37 of them would get a positive result and the others would get a falsely negative result.\n\nOn the surface, this would seem concerning and would likely explain why many people have reported testing negative at first only to then be diagnosed with COVID-19 a few days later. But, it’s important to point out the test sensitivity does vary between studies and another unpublished [study](https:\/\/www.medrxiv.org\/content\/10.1101\/2022.01.08.22268954v2.full) not included in that review found that the sensitivity of the tests with respect to Omicron ranged between 65 and 95 percent in the different patient populations. Also, while test sensitivity was low overall, it was over 80 percent after Day 3 of the infection and improved considerably with repeat testing.\n\nWhether the genetic changes in new variants are having an impact on test accuracy is not entirely clear. Part of the problem is that the predictive value of test changes as disease prevalence changes. As diseases become more common, the relative number of true positives vs. false positives shifts and we get fewer false positives but consequently more false negatives. So as COVID cases surge, we must expect more false negatives, for purely mathematical reasons.\n\nThe solution, though, is clear. If you think you have COVID and test negative, you need to test again.\n***\n[@DrLabos](http:\/\/twitter.com\/drlabos)","meta_canonical":null}

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5. Seen Status Check

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CRAWLED

7 days ago

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Page Info Filters

Filter	Status	Condition	Details
HTTP status	PASS	`download_http_code = 200`	HTTP 200
Age cutoff	PASS	`download_stamp > now() - 6 MONTH`	0.2 months ago
History drop	PASS	`isNull(history_drop_reason)`	No drop reason
Spam/ban	PASS	`fh_dont_index != 1 AND ml_spam_score = 0`	ml_spam_score=0
Canonical	PASS	`meta_canonical IS NULL OR = '' OR = src_unparsed`	Not set

Page Details

Property	Value
URL	https://www.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests
Last Crawled	2026-04-04 16:33:59 (7 days ago)
First Indexed	2022-04-05 19:06:59 (4 years ago)
HTTP Status Code	200
Meta Title	Navigating False Negatives on COVID Rapid Tests - McGill University
Meta Description	If you think you have COVID and test negative, you need to test again.
Meta Canonical	null
Boilerpipe Text	This article was originally posted in the Montreal Gazette . It should be clear by this point that we are in a sixth wave driven by the BA.2 variant. With COVID cases and hospitalizations rising, it still remains somewhat unclear how high they will go and how long it will last. But what is stymying many people this time around and making the whole issue more complicated is the issue of testing. After the fifth wave, widespread PCR testing stopped because the system simply couldn’t cope. Rapid tests became, out of necessity, the standard testing strategy for the general population. There are obviously several advantages to rapid tests. They are cheaper, more widely available, can be done at home and do not require medical personnel to administer them. But, there is the issue of test accuracy. False positives with rapid tests are extremely rare, with one research letter in JAMA pegging the false positivity rate at 0.05% and many of these false positives were traced back to a single batch of tests, which suggests it was a specific quality control issue rather than a question of decreased test accuracy. But while false positives are rare, false negatives are not. It seems, from anecdotal experience, that we are seeing more false negatives during this wave, which has led to speculation that the tests may not perform as well against the Omicron variant and now BA.2. (The new variant has not been around long enough to generate enough data, but the assumption is that it would behave the same way as Omicron, given their similarity.) There is a theoretical basis for this concern. The Omicron variant in particular had mutations on the S-gene that coded for the spike protein and might not be detected by some laboratory tests. The U.S. Food and Drug Administration keeps an ongoing list of specific test kits that may have issues with new variants, but don’t specifically mention any rapid tests that have issues with the Omicron variant. The FDA does say, “early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” but does not raise any specific issues or provide any data. The Ontario Science Table did review the sensitivity of rapid tests against the Delta and Omicron variants and found, in unpublished studies, that the sensitivity against Omicron was clearly lower than it was for Delta. Its analysis suggested that the sensitivity of rapid tests to detect the Omicron variant was 37 percent, compared to 81 percent for Delta. In effect, this means that if 100 people had COVID and were infected with the Omicron variant, only 37 of them would get a positive result and the others would get a falsely negative result. On the surface, this would seem concerning and would likely explain why many people have reported testing negative at first only to then be diagnosed with COVID-19 a few days later. But, it’s important to point out the test sensitivity does vary between studies and another unpublished study not included in that review found that the sensitivity of the tests with respect to Omicron ranged between 65 and 95 percent in the different patient populations. Also, while test sensitivity was low overall, it was over 80 percent after Day 3 of the infection and improved considerably with repeat testing. Whether the genetic changes in new variants are having an impact on test accuracy is not entirely clear. Part of the problem is that the predictive value of test changes as disease prevalence changes. As diseases become more common, the relative number of true positives vs. false positives shifts and we get fewer false positives but consequently more false negatives. So as COVID cases surge, we must expect more false negatives, for purely mathematical reasons. The solution, though, is clear. If you think you have COVID and test negative, you need to test again. @DrLabos
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[Sign-Up Here](https://e1.envoke.com/ext/pages/4244cddff96d640b64864b5906677412) [Home](https://www.mcgill.ca/oss/) # Navigating False Negatives on COVID Rapid Tests If you think you have COVID and test negative, you need to test again. ![](https://www.mcgill.ca/oss/files/oss/styles/hd/public/test-g8be875e96_1920.jpeg?itok=YUvCrveb&timestamp=1649185364) [Christopher Labos MD, MSc](https://www.mcgill.ca/oss/articles-by-author/Christopher%20Labos%20MD,%20MSc) \\| 5 Apr 2022 [COVID-19](https://www.mcgill.ca/oss/category/article-categories/covid-19) - [Add to calendar](https://www.mcgill.ca/oss/node/9073/ical "Add to calendar") - [Facebook](http://www.facebook.com/sharer.php?u=https%3A//www.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests&t=Navigating%20False%20Negatives%20on%20COVID%20Rapid%20Tests "Share on Facebook") - [LinkedIn](http://www.linkedin.com/shareArticle?mini=true&url=https%3A//www.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests&title=Navigating%20False%20Negatives%20on%20COVID%20Rapid%20Tests&summary=%0D%0AThis%20article%20was%20originally%20posted%20in%20the%20Montreal%20Gazette.&source=Office%20for%20Science%20and%20Society%20 "Publish this post to LinkedIn") - [Tweet Widget](http://twitter.com/share?url=https%3A//www.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests&count=horizontal&via=McGillOSS&text=Navigating%20False%20Negatives%20on%20COVID%20Rapid%20Tests&counturl=https%3A//www.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests "Tweet This") *** This article was originally posted in the [Montreal Gazette](https://montrealgazette.com/opinion/columnists/christopher-labos-navigating-false-negatives-on-covid-rapid-tests). * It should be clear by this point that [we are in a sixth wave](https://montrealgazette.com/news/local-news/quebec-now-officially-in-pandemics-sixth-wave-inspq-says) driven by the BA.2 variant. With COVID cases and hospitalizations rising, it still remains somewhat unclear how high they will go and how long it will last. But what is stymying many people this time around and making the whole issue more complicated is the issue of testing. After the fifth wave, widespread PCR testing stopped because the system simply couldn’t cope. Rapid tests became, out of necessity, the standard testing strategy for the general population. There are obviously several advantages to rapid tests. They are cheaper, more widely available, can be done at home and do not require medical personnel to administer them. But, there is the issue of test accuracy. False positives with rapid tests are extremely rare, with one research letter in [JAMA](https://jamanetwork.com/journals/jama/fullarticle/2788067) pegging the false positivity rate at 0.05% and many of these false positives were traced back to a single batch of tests, which suggests it was a specific quality control issue rather than a question of decreased test accuracy. But while false positives are rare, false negatives are not. It seems, from anecdotal experience, that we are seeing more false negatives during this wave, which has led to speculation that the tests may not perform as well against the Omicron variant and now BA.2. (The new variant has not been around long enough to generate enough data, but the assumption is that it would behave the same way as Omicron, given their similarity.) There is a theoretical basis for this concern. The Omicron variant in particular had mutations on the S-gene that coded for the spike protein and might not be detected by some laboratory tests. The U.S. Food and Drug Administration keeps an ongoing [list](https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/sars-cov-2-viral-mutations-impact-covid-19-tests#omicronbackground) of specific test kits that may have issues with new variants, but don’t specifically mention any rapid tests that have issues with the Omicron variant. The FDA does say, “early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” but does not raise any specific issues or provide any data. The Ontario Science Table did [review](https://covid19-sciencetable.ca/sciencebrief/use-of-rapid-antigen-tests-during-the-omicron-wave/) the sensitivity of rapid tests against the Delta and Omicron variants and found, in unpublished studies, that the sensitivity against Omicron was clearly lower than it was for Delta. Its analysis suggested that the sensitivity of rapid tests to detect the Omicron variant was 37 percent, compared to 81 percent for Delta. In effect, this means that if 100 people had COVID and were infected with the Omicron variant, only 37 of them would get a positive result and the others would get a falsely negative result. On the surface, this would seem concerning and would likely explain why many people have reported testing negative at first only to then be diagnosed with COVID-19 a few days later. But, it’s important to point out the test sensitivity does vary between studies and another unpublished [study](https://www.medrxiv.org/content/10.1101/2022.01.08.22268954v2.full) not included in that review found that the sensitivity of the tests with respect to Omicron ranged between 65 and 95 percent in the different patient populations. Also, while test sensitivity was low overall, it was over 80 percent after Day 3 of the infection and improved considerably with repeat testing. Whether the genetic changes in new variants are having an impact on test accuracy is not entirely clear. Part of the problem is that the predictive value of test changes as disease prevalence changes. As diseases become more common, the relative number of true positives vs. false positives shifts and we get fewer false positives but consequently more false negatives. So as COVID cases surge, we must expect more false negatives, for purely mathematical reasons. The solution, though, is clear. If you think you have COVID and test negative, you need to test again. * [@DrLabos](http://twitter.com/drlabos) Keywords: [rapid test](https://www.mcgill.ca/oss/category/tags/rapid-test) [antigen test](https://www.mcgill.ca/oss/category/tags/antigen-test) [false negative](https://www.mcgill.ca/oss/category/tags/false-negative) [false positive](https://www.mcgill.ca/oss/category/tags/false-positive) [Covid](https://www.mcgill.ca/oss/category/tags/covid) [sixth wave](https://www.mcgill.ca/oss/category/tags/sixth-wave) [Omicron variant](https://www.mcgill.ca/oss/category/tags/omicron-variant) [BA.2](https://www.mcgill.ca/oss/category/tags/ba2) ## What to read next ## [TZLA Plasma Healing: The Anarcho-Capitalist Cure-All 26 Mar 2026](https://www.mcgill.ca/oss/article/covid-19-medical-critical-thinking-pseudoscience/tzla-plasma-healing-anarcho-capitalist-cure-all " TZLA Plasma Healing: The Anarcho-Capitalist Cure-All") ![](https://www.mcgill.ca/oss/files/oss/styles/large/public/banner_for_tzla_v2.png?itok=hMci-7BU) ## [Rare Blood Clots After Certain COVID Vaccines, Explained 19 Feb 2026](https://www.mcgill.ca/oss/article/covid-19-medical-health-and-nutrition-technology/rare-blood-clots-after-certain-covid-vaccines-explained "Rare Blood Clots After Certain COVID Vaccines, Explained") ![](https://www.mcgill.ca/oss/files/oss/styles/large/public/banner_for_covid_vaccine_blood_clots_v1.png?itok=ZIoP4W7c) ## [The Strange Story of Nicotine Patches to Treat Long COVID 20 Nov 2025](https://www.mcgill.ca/oss/article/medical-health-and-nutrition-pseudoscience/strange-story-nicotine-patches-treat-long-covid "The Strange Story of Nicotine Patches to Treat Long COVID") ![](https://www.mcgill.ca/oss/files/oss/styles/large/public/banner_for_nicotine_v1.jpg?itok=P6K1pR2j) ## [Everyone Else Is Lying to You: A Damning Archive of Science Denial 16 Oct 2025](https://www.mcgill.ca/oss/article/pseudoscience-reviews/everyone-else-lying-you-damning-archive-science-denial "Everyone Else Is Lying to You: A Damning Archive of Science Denial") ![](https://www.mcgill.ca/oss/files/oss/styles/large/public/banner_for_everyone_else_is_lying_to_you_v1.jpg?itok=TJRsDZ7-) ## [How We Know that Vaccines Are Safe 21 Feb 2025](https://www.mcgill.ca/oss/article/covid-19-medical-critical-thinking/how-we-know-vaccines-are-safe "How We Know that Vaccines Are Safe") ![](https://www.mcgill.ca/oss/files/oss/styles/large/public/vax.png?itok=AZKsB4Bv) ## [Bret Weinstein, Would-Be Galileo 27 Sep 2024](https://www.mcgill.ca/oss/article/covid-19-critical-thinking/bret-weinstein-would-be-galileo "Bret Weinstein, Would-Be Galileo") ![](https://www.mcgill.ca/oss/files/oss/styles/large/public/weinstein_banner_image_v1.jpg?itok=EDFuF-ZO) [Back to top](https://www.mcgill.ca/oss/article/covid-19/navigating-false-negatives-covid-rapid-tests) ## Department and University Information ## Office for Science and Society McGill University 801 Sherbrooke Street West Montreal, Quebec H3A 0B8 ![Office for Science and Society ](https://www.mcgill.ca/oss/files/oss/moriarty_branding_img.jpg) [Facebook](https://www.facebook.com/McGillOSS "Follow us on Facebook") [YouTube](http://www.youtube.com/mcgilloss "Follow us on YouTube") [Instagram](https://www.instagram.com/mcgilloss/ "Follow us on Instagram") [Bluesky](https://bsky.app/profile/mcgilloss.bsky.social "Follow us on Bluesky") [McGill University](https://www.mcgill.ca/ "return to McGill University") Copyright © 2026 McGill University [Accessibility](https://www.mcgill.ca/accessibility "Accessibility") [Cookie notice](https://www.mcgill.ca/cookie-notice "Cookie notice") Cookie settings [Log in](https://www.mcgill.ca/oss/saml_login?destination=node/9073)
Readable Markdown	*** This article was originally posted in the [Montreal Gazette](https://montrealgazette.com/opinion/columnists/christopher-labos-navigating-false-negatives-on-covid-rapid-tests). * It should be clear by this point that [we are in a sixth wave](https://montrealgazette.com/news/local-news/quebec-now-officially-in-pandemics-sixth-wave-inspq-says) driven by the BA.2 variant. With COVID cases and hospitalizations rising, it still remains somewhat unclear how high they will go and how long it will last. But what is stymying many people this time around and making the whole issue more complicated is the issue of testing. After the fifth wave, widespread PCR testing stopped because the system simply couldn’t cope. Rapid tests became, out of necessity, the standard testing strategy for the general population. There are obviously several advantages to rapid tests. They are cheaper, more widely available, can be done at home and do not require medical personnel to administer them. But, there is the issue of test accuracy. False positives with rapid tests are extremely rare, with one research letter in [JAMA](https://jamanetwork.com/journals/jama/fullarticle/2788067) pegging the false positivity rate at 0.05% and many of these false positives were traced back to a single batch of tests, which suggests it was a specific quality control issue rather than a question of decreased test accuracy. But while false positives are rare, false negatives are not. It seems, from anecdotal experience, that we are seeing more false negatives during this wave, which has led to speculation that the tests may not perform as well against the Omicron variant and now BA.2. (The new variant has not been around long enough to generate enough data, but the assumption is that it would behave the same way as Omicron, given their similarity.) There is a theoretical basis for this concern. The Omicron variant in particular had mutations on the S-gene that coded for the spike protein and might not be detected by some laboratory tests. The U.S. Food and Drug Administration keeps an ongoing [list](https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/sars-cov-2-viral-mutations-impact-covid-19-tests#omicronbackground) of specific test kits that may have issues with new variants, but don’t specifically mention any rapid tests that have issues with the Omicron variant. The FDA does say, “early data suggests that antigen tests do detect the Omicron variant but may have reduced sensitivity,” but does not raise any specific issues or provide any data. The Ontario Science Table did [review](https://covid19-sciencetable.ca/sciencebrief/use-of-rapid-antigen-tests-during-the-omicron-wave/) the sensitivity of rapid tests against the Delta and Omicron variants and found, in unpublished studies, that the sensitivity against Omicron was clearly lower than it was for Delta. Its analysis suggested that the sensitivity of rapid tests to detect the Omicron variant was 37 percent, compared to 81 percent for Delta. In effect, this means that if 100 people had COVID and were infected with the Omicron variant, only 37 of them would get a positive result and the others would get a falsely negative result. On the surface, this would seem concerning and would likely explain why many people have reported testing negative at first only to then be diagnosed with COVID-19 a few days later. But, it’s important to point out the test sensitivity does vary between studies and another unpublished [study](https://www.medrxiv.org/content/10.1101/2022.01.08.22268954v2.full) not included in that review found that the sensitivity of the tests with respect to Omicron ranged between 65 and 95 percent in the different patient populations. Also, while test sensitivity was low overall, it was over 80 percent after Day 3 of the infection and improved considerably with repeat testing. Whether the genetic changes in new variants are having an impact on test accuracy is not entirely clear. Part of the problem is that the predictive value of test changes as disease prevalence changes. As diseases become more common, the relative number of true positives vs. false positives shifts and we get fewer false positives but consequently more false negatives. So as COVID cases surge, we must expect more false negatives, for purely mathematical reasons. The solution, though, is clear. If you think you have COVID and test negative, you need to test again. * [@DrLabos](http://twitter.com/drlabos)
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