WASHINGTON | Antigenic tests for COVID-19, which have the advantage of delivering a result in just a few minutes, are less sensitive to the Omicron variant than to previous variants, US health authorities warned on Tuesday.
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This means that these tests are likely to indicate a negative result despite an infection – the famous false negatives – if a person is infected with Omicron.
“Preliminary data suggests that antigenic tests detect the Omicron variant well, but with reduced sensitivity,” the US Medicines Agency (FDA) said in a statement.
However, she specified that she would continue to authorize their use, following the precise instructions for use.
“If a person is tested negative with an antigen test, but is suspected of having COVID-19, for example having symptoms or a high probability of infection from exposure, follow-up with a molecular test ( or PCR, Editor’s note) is important, ”said the agency.
Antigen tests detect antigens on the surface of the virus, while PCR tests look for the genetic material of the virus. The first were already less sensitive than the second, recalls the FDA.
And their sensitivity is now affected due to the many mutations of the Omicron variant.
Even so, antigen tests, sometimes called rapid tests, are widely promoted by experts because they can be done regularly at home for little cost and thus help control the epidemic.
In the United States, these increasingly popular home test kits have recently become scarce with the sharp rise in Omicron-related contaminations and with the holiday season.
Last week, President Joe Biden announced the purchase of 500 million rapid home tests, which can be ordered by Americans through a dedicated website, starting in January.