US health officials warned Tuesday that rapid tests for COVID-19, which feature a result in just a few minutes, are less sensitive to the Omicron variant than previous variants.
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This means that these tests are more likely to indicate a negative result despite the infection – the notorious false negatives – if the person has omicron.
“Preliminary data indicate that antigen tests detect the Omicron variant well, but with low sensitivity,” the FDA said in a statement.
However, it has specified that it will continue to allow its use, following the exact instructions for use.
“If a person tests negative with an antigen test, but suspects they have COVID-19, eg develop symptoms or a high probability of infection from exposure, follow-up with molecular testing (or PCR, editor’s note) is important,” the agency said.
Antigen tests detect the presence of antigens on the surface of the virus, while polymerase chain reaction (PCR) tests look for the virus’ genetic material. The first was already less allergic than the second, the FDA recalls.
Their sensitivity is now affected by the many mutations of the Omicron variant.
However, antigen tests, sometimes called rapid tests, are widely promoted by experts because they can be done regularly at home at little cost, thus helping to control the epidemic.
In the United States, these increasingly popular home test kits have become rare recently with the sharp rise in omicron-related contaminations and with the holiday season.
Last week, President Joe Biden announced the purchase of 500 million take-home rapid tests, which Americans can order through a dedicated website, starting in January.
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