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Rapid antigen tests can't detect an Omicron infection fast enough to prevent community spread, new study finds

A new rapid antigen test by Roche (image: Roche)
A new rapid antigen test by Roche (image: Roche)
Rapid antigen tests may be a waste as far as the fast-spreading new COVID-19 Omicron virus variant is concerned, says a new scientific study. The researchers followed frontline workers whose jobs require daily testing with PCR and rapid antigen tests, and found out that most of them have been shedding Omicron virus particles long before it showed on the rapid antigen tests, while PCR tests caught the infection much earlier.

Rapid COVID-19 virus testing requirements are proliferating as one stopgap measure to restrict the spread of the new Omicron variant. Quick antigen tests are often mandated for gaining access to fitness clubs, restaurants, or simply so as you can get to your workplace. Unfortunately, in these times of an extremely contagious Omicron variant, rapid antigen tests may turn out to be a waste of time and resources. A new study that was just uploaded to the MedRxiv database, found out that rapid antigen tests can't detect a present Omicron infection fast enough to limit the spread of the virus, as they reacted on an infection much later than PCR tests, and long after that person was able to infect others or was showing any symptoms.

The researchers looked at "a high-risk occupational case cohort of 30 individuals with daily testing during an Omicron outbreak in December 2021," noting that the nature of the people's jobs required both PCR and antigen testing. The subjects were gathered from five different frontline workplaces in New York City based on the fact that they have at some point tested positive for the Omicron variant. What the study found was that "based on viral load and transmissions confirmed through epidemiological investigation, most Omicron cases were infectious for several days before being detectable by rapid antigen tests." Those who took PCR tests, however, were able to catch their infection much sooner, possibly before they were able to go out and about shedding the virus unwittingly.

The rapid antigen tests that the research subjects used were Abbott BinaxNOW and Quidel QuickVue, both having an FDA approval, just as the recently announced Roche self-test antigen kit that boasts both Omicron and Delta sensitivity. As often happens with quick COVID-19 tests, however, the antigen reaction is only strong enough well into an infection when the person begins to show the first symptoms. It seems that the Omicron variant, despite evidence of being less lethal, won't be an exception when it comes to evading antigen test detection. "The median time from first positive PCR to first detectable antigen positive was three days," report the scientists, while the person had high enough virus load detected by the PCR test that they were able to infect others from Day 1.

Since Omicron lodges in the nose and throat, rather than just stopping there on the way to the lungs like Delta, some epidemiologists suggest to augment the antigen testing procedure for it. The new study warns about the ability of rapid tests to detect Omicron soon enough, but lists that only "nasal rapid antigen test results" were used. If you want to raise the odds of present Omicron virus variant detection for your antigen test of choice, a throat swab may be added to the nasal one, too, thus increasing the chance of earlier detection to a much more palatable level when compared with the more sensitive but also more expensive and much slower PCR test.

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FDA-approved antigen tests were falsely negative up to 3 days after a PCR-confirmed Omicron infection strong enough to shed the COVID-19 virus to others.

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> Notebook / Laptop Reviews and News > News > News Archive > Newsarchive 2022 01 > Rapid antigen tests can't detect an Omicron infection fast enough to prevent community spread, new study finds
Daniel Zlatev, 2022-01- 7 (Update: 2022-01- 7)