Some antigen tests, including the rapid COVID-19 test made by the Abbott BinaxNOW and Quidel QuickVue brands, may fail to detect if you have omicron, according to new data released this week.
In December, Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, warned that antigen tests (also known as rapid COVID tests, or home COVID tests), may miss omicron infections, as SELF reported.
“Some, and many of the commonly used ones, appear to pick up and detect omicron quite well,” Dr. Fauci said at the time. “We’re in the process of doing large screening to determine which of these antigen point-of-care rapid tests still maintain their accuracy of diagnosis.”
We now have more real-world data, based on the commonly used Abbott BinaxNOW and Quidel QuickVue antigen tests. According to the new study, these rapid tests may not detect omicron even when you have a high viral load (meaning you’re contagious), according to the New York Times. In the small study, which has not yet been peer-reviewed, researchers from the COVID-19 Sports and Society Working Group looked at data from 30 people who worked in a high-risk setting during the December omicron outbreak. They were tested daily, using both rapid COVID-19 tests taken via nasal swab and PCR tests taken via saliva sample. “Most omicron cases were infectious for several days before being detectable by rapid antigen tests,” the authors wrote.
Once a person had received a positive PCR test, it took an average of three days for the antigen test to also come back positive. For those of us taking rapid COVID-19 tests at home, that’s three days in which it would be possible to unknowingly spread omicron. In fact, in four cases included in the study, individuals infected other people while their rapid tests came back negative, the Times reports.
This doesn’t mean you should stop using home tests. The report comes a week after the Food and Drug Administration released new guidelines on using rapid COVID-19 tests to address concerns that they do not accurately detect omicron. “Early data suggests that antigen tests do detect the omicron variant but may have reduced sensitivity,” the agency wrote. They added that individuals should still continue to use them—rapid tests may be less likely to pick up early infections, but they can still be a useful tool.
“In following the FDA’s long-standing rapid test recommendations, if a person tests negative with an antigen test but is suspected of having COVID-19, such as experiencing symptoms or have a high likelihood of infection due to exposure, follow-up molecular testing is important for determining a COVID-19 infection,” the guidelines state. “If a person tests positive with an antigen test, they should self-isolate and seek follow-up care with a health care provider to determine the next steps.”
If you do test positive using an at-home antigen test, health experts stress that you should report your result to your doctor and your local health department, per a report from CNN. Doing so helps health officials maintain accurate case counts. “With all the self-testing going on, we really don’t have a good number of the case counts,” Georges Benjamin, M.D., the executive director of the American Public Health Association said in an interview with CNN. “It is clear we’re underreporting [COVID-19 cases].”
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