Why health experts still back at-home antigen tests after FDA pegs them 'less sensitive' to omicron

Dr. Fauci says if you want the most accurate results, you should take a PCR test.

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Thursday, December 30, 2021
FDA says at-home antigen tests 'less sensitive' to omicron
Dr. Fauci says at-home COVID antigen tests are still useful, even after the FDA said they're "less sensitive" to omicron.

SAN JOSE, Calif. (KGO) -- New rapid at-home tests could be at stores soon, after the FDA approved two additional brands.

However, there are questions about how effective those antigen tests are at detecting the omicron variant.

We are just days away from the New Year and many are still on the hunt, hoping to get their hands on a quick at-home antigen test. That demand has now been met with a new FDA discovery.

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The agency found that while antigen tests detected the omicron variant, they did so with "less sensitivity," finding it's possible such tests could miss an infection.

"They never have been 100% sensitive," Dr. Anthony Fauci told ABC News. "If you want to definitively find out if someone is infected- for example, if someone has symptoms and has reason to believe they're infected, the test to use is a PCR test."

Lab-based PCR tests are more sensitive and have a turnaround time of up to 72-hours.

Dr. Fauci said although sensitivity is somewhat diminished with antigen tests, they're still a useful tool for broad surveillance.

VIDEO: What to know about rapid COVID at-home tests as demand for testing surges

The demand for COVID-19 testing has surged as President Biden is making 500 million free rapid tests available to Americans next month.

UCSF Epidemiologist Dr. George Rutherford said antigen tests are reliable with no variant-to-variant variability.

"The tricky part is just timing," Dr. Rutherford said. "And omicron, may have a shorter incubation period than the prior variants. And that's one of the reasons that the isolation period has gotten shrunk down."

Rapid antigen tests are relatively inexpensive and offer results in about 15 minutes. They work by detecting surface proteins of the coronavirus.

Most popular self-tests tell people to take two tests on separate days for more accurate results.

"The bottom line is that these are very reliable tests. They're testing for exactly the same thing- for every strain, there's no variant-to-variant variability," Dr. Rutherford added. "They're looking at individual proteins that don't have anything to do with where the mutations are."

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ABC7 News Special Correspondent Dr. Alok Patel said, "An antigen test - if you can get your hands on one - should be taken right before a potential gathering where you're going to see people. That's like a snapshot in time."

"You want to take it right before you walk in the door of a gathering," he added.

On Wednesday, came word of two new over the counter at-home antigen tests, authorized by the FDA.

One test is manufactured by SD Biosensor and distributed by Roche. It was authorized on December 24.

The other test is the Siemens. It was authorized on December 29.

VIDEO: Free at-home COVID rapid tests: What to know about Biden's plan to deliver 500 million kits

President Biden announced a plan on Tuesday to distribute 500 million free at-home rapid tests to Americans beginning in January along with more COVID fighting strategy.

The US Department of Health and Human Services said the authorizations will bring tens-of-millions of new tests per month, across the country.

"This is the time for more testing, not less testing," said Dr. Rutherford.

The FDA says "studies are underway" to understand why the Omicron variant might impact rapid tests.