US health officials warned Tuesday that antigenic screening tests for COVID-19, which have the advantage of producing results within minutes, are less sensitive to the Omicron variant.

This means that these tests are more likely to indicate a negative result regardless of infection — the notorious false negative — if a person is infected with Omicron.

“Preliminary data suggest that antigenic tests detect the omicron variant well, but with low sensitivity,” the US Medicines Agency (FDA) said in a statement.

However, she specified that she would continue to authorize their use, following the exact instructions for use.

“If a person tests negative with an antigen test, but is suspected of having Covid-19, eg with symptoms or exposure to high likelihood of infection, follow-up with molecular testing (or PCR, editor’s note) is important. is,” the agency said.

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, the FDA recalls.

And their susceptibility is now affected due to multiple mutations of the Omicron variant.

Nevertheless, antigen testing, sometimes called rapid testing, is widely promoted by experts because they can be routinely performed at home at low cost and thus help in controlling epidemics. Is.

In the United States, these increasingly popular home test kits have recently ended with a very sharp increase in contamination associated with Omicron and the year-end celebrations.

Last week, President Joe Biden announced the purchase of 500 million take-home rapid tests that could be ordered by Americans starting in January through a dedicated website.