The surge of the Omicron variant has raised concerns over the  efficacy of  at-home  rapid Covid tests that are rapidly gaining popularity in the battle against the pandemic.

Health officials  have warned that at-home antigen COVID-19 tests may be less effective at detecting cases of the Omicron variant  that’s currently swarming parts of the word – compared to other strains.

The US Food and Drug Administration (FDA) said early data suggest that antigen tests do detect the Omicron variant but may have reduced sensitivity.

For someone infected with the Omicron variant, some antigen tests may be more likely to provide a false negative result than if they had Delta.  Until the issue is resolved, the FDA says the  antigen tests are “expected to fail to detect” the Omicron variant.

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The FDA still advises people to use antigen tests just as before, although it notes that the most accurate tests available are the  PCR tests, which detect tiny snippets of the virus’s genetic material.  PCR tests require specialized lab equipment, so results can be delayed, particularly when there are surges, as demand grows.

Rapid tests, on the other hand, detect molecules  found on the virus’s surface, called antigens. They’re not as accurate, but they can be run at home and provide results in 15 minutes.

The tests are most accurate when a person has symptoms, studies suggest. While they are able to detect asymptomatic cases, there’s a greater likelihood for false negatives.

Experts say it takes more virus for the antigen test to be positive than it does for the PCR to be positive, implying that a person is more infectious if  antigen-tested-positive.

The increased demand for tests coincides with the growing number of COVID-19  cases, including breakthrough infections among the vaccinated, as many people try to avoid the rapid spread of the omicron variant.