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Los Angeles County will no longer provide a commonly used coronavirus test at its pop-up testing sites after federal regulators raised concerns about its accuracy, health officials said Sunday. 

The decision only affects mobile testing sites administered by the county and comes after the U.S. Food and Drug Administration said in a safety communication last week that the oral swab COVID-19 tests produced by the start-up Curative carry a “risk of false results, particularly false-negative results.”

The risk is especially higher when it’s used on people not experiencing symptoms. The FDA says the tests could lead to infected people having a false sense of security, increasing the risk of spread. People who don’t believe they’re sick could also be delayed in seeking treatment.

The use of Curative tests at eight drive-through testing sites and six mobile locations operated by the city of Los Angeles and those run by other organizations are unaffected by Sunday’s decision. However, testing is expected to temporarily decrease after Mayor Eric Garcetti’s office announced separately that the Dodger Stadium — the county’s largest testing site — would be turned into a vaccine center this week. Testing operations at the stadium will end Monday.

Mayor Eric Garcetti defended the tests on Thursday, prior to the county’s announcement, saying that he still trusted the tests “deeply.” He said the FDA’s message was “a very vague warning didn’t have data behind it,” and he doesn’t see a reason to stop using the tests since  they are effective at catching cases in people who are asymptomatic.

The mayor said the tests have identified infections in 92,000 asymptomatic people — a third of all positive cases.

The FDA originally granted emergency authorization to the Curative tests in April. However, the company and the FDA recommended that the test should be given only to symptomatic people within 14 days of COVID-19 symptom onset, and the swab must be administered under the guidance of a trained medical professional. 

“When the test is not performed in accordance with its authorization or as described in the authorized labeling, there is a greater risk that the results of the test may not be accurate,” the FDA wrote in its message.

L.A. County’s testing sites had originally used the Curative oral-swab tests but in June switched to only using nasal tests, citing a concern with false negatives.

In mid-December, however, Curative started providing tests at county-supported pop-up testing sites, according to county health officials.

Between Dec. 13 and Jan. 2, about 10% of all the coronavirus tests administered at those county sites were Curative tests, the County Department of Health and Human Services said in a statement Sunday.

The county said Sunday as a precaution it will stop using the Curative tests at its sites and will instead use tests by Fulgent Genetics.

County officials said they were discontinuing the use of the Curative tests “as a precaution” and would replace them with tests by Fulgent Genetics.

Health officials said that any type of test poses a risk of false negatives, because the results rely on how well the saliva sample was collected and the viral concentration that it may contain.

“There is no reliable way to detect early infection, meaning that infection often spreads before symptoms develop,” the statement said.Nevertheless, county officials said the Curative tests “remain better at detecting disease than other tests, including rapid tests.”