Covid-19 rapid tests not as accurate with Omicron, US regulator says


Rapid home tests for Covid are more likely to give a false negative with the highly mutated Omicron variant compared to previous strains, the United States Food and Drug Administration (FDA) said on Tuesday.

The news comes as the country faces a massive increase in cases that experts say are under-captured due to a testing crisis, with long wait times for the most accurate PCR tests and extremely limited home kits.

In a statement, the FDA said it was working with the National Institutes of Health (NIH) to study the performance of home tests, also known as “antigen” tests, on patient samples containing live versions. of the Omicron variant.

“The first data suggests that antigen tests detect the Omicron variant but may have reduced sensitivity,” the agency said.

Sensitivity is a measure of the likelihood that a test will be able to detect a positive result.

Previous testing had focused on heat-inactivated virus samples, rather than live viruses, which is better, and a drop in performance had not been seen so far, the statement added.

The FDA has said it will continue to allow the use of antigen tests – which work by detecting the surface proteins of the coronavirus – and that individuals should continue to use them as directed.

For example, some rapid tests require users to take two tests, at a certain time interval, in order to confirm a negative result.

If a person is negative with a rapid test but is believed to be likely to have Covid, either because of symptoms or their exposures, it is still recommended that they take a ‘benchmark’ molecular test – like PCR.

These detect the genetic material of the virus. They are more precise because they can make millions of copies of the virus’s RNA, so even small amounts become detectable.



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