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Antigen COVID tests may be less sensitive to omicron variant, FDA says

On top of the rapid tests already being less sensitive in general, the FDA now says they are also less sensitive to the new variant.

HOUSTON — The omicron variant of COVID-19 is proving to be an entirely new battle and the U.S. Food and Drug Administration is learning one of the tools we have to detect it may not work as well against omicron.

The FDA said it has learned the antigen test is less sensitive to the newest variant.

Before we dive into what doctors say you should do, let’s look at the difference between PCR and antigen tests.

The PCR test is the more common, molecular test that’s more accurate, but results take longer.

With the antigen test, or as many call the rapid test, results can come back in minutes but they are generally less accurate than the PCR.

Now, let’s talk about omicron.

On top of rapid tests already being less sensitive in general, the FDA now says they are also less sensitive to the new variant.

“That means that people are likely to test false negative sometimes," UT Health Houston and Memorial Hermann Infectious Diseases Expert Dr. Luis Ostrosky said.

Ostrosky said that doesn’t mean you can’t take a rapid test.

“If you have symptoms, you can try an antigen test and if it’s positive, you made the diagnosis," Ostrosky said.

But if you test negative, he says don't stop there.

“We ask people to do either serial retesting with antigen or just go ahead and get a PCR which is a definitive answer," Ostrosky said.

Serial retesting, he said, is retaking the rapid test a few days in a row. But if you only have the one test, still wear your mask and keep your distance.

And we know Texans are taking the rapid test, as nearly 10 million have been reported to the state.

But omicron is now adding a little more uncertainty to those results.

“The two explanations for this would be a lower viral load for omicron or a mismatch between the antigens that omicron has and the ones we’re trying to detect with the kits," Ostrosky said.

Hopefully, the uncertainty won’t last long.

Ostrosky said the manufacturers of rapid tests are always working to make them more precise.

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