Rapid COVID-19 tests are less accurate with omicron, US warns

Rapid home tests are more likely to COVID-19 show false negative with the omicron variant, strongly mutated with respect to previous strains, reported the US Food and Drug Administration (FDA).

The news comes as the country faces a huge increase in cases that, according to experts, are being underdiagnosed due to the crisis of access to tests, with long wait times for the most accurate tests such as PCR and extremely scarce home kits. .

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

“Early data suggest that antigen tests detect the omicron variant, but may have reduced sensitivity,” the agency added.

Sensitivity is a measure that estimates the probability that a test will detect a positive result.

Previous tests had focused on heat-inactivated virus samples, rather than live virus, which is better, and so far no drop in performance has been detected, the statement added.

The FDA said it would continue to authorize the use of antigen tests, which work by detecting coronavirus surface proteins, and that people should continue to use them according to instructions.

For example, some rapid tests instruct users to run two tests, with a certain time interval, to confirm a negative result.

If a person tests negative on a rapid test, but is thought likely to have COVID-19, either from symptoms or from their exposures, it is recommended that a “gold standard” molecular test, such as PCR, be performed.

These types of tests detect the genetic material of the virus. They are more accurate because they can produce millions of copies of the virus’s RNA, so even small amounts are detectable.