San Dimas-based diagnostics firm Curative, whose coronavirus tests are widely used across the country — including at Los Angeles sites — is defending the validity of its tests Thursday, following a federal government alert about the possibility of false negative results.

The Food and Drug Administration issued the alert Monday, warning of the potential for Curative tests to wrongly come back negative. It did not give any indication about the breadth of the problem, or how often such false results occur.

But the agency warned that the test must be administered in accordance with its authorized use — which limits it to use on people who are showing symptoms of COVID-19. Testing in Los Angeles is open to people regardless of whether they are showing symptoms.

Mayor Eric Garcetti on Thursday defended the Curative tests, saying administering them on asymptomatic people has allowed the city catch the virus in 92,000 people who would have gone undetected otherwise.

“One-third of the tests that we’ve tested and found positive are asymptomatic people, and I’m not going to ever apologize because there was, I think, a lot of debate about whether asymptomatic people should be tested or not,” Garcetti said.

“The choice is whether we find those 92,000 or not. It’s not like there’s some other tests that FDA says is better or that’s working better on asymptomatic (people),” he said. “I’d rather do it and continue to push forward with finding those tens of thousands of people that every single month we are finding who are asymptomatic.”

He reminded test takers to cough vigorously three to five times before swabbing their mouth, but added that PCR tests are never 100% accurate and should not be viewed as a free pass to ignore public health directives.

According to the FDA alert, “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 many not be accurate.”

It also states that collection of specimens “must be directly observed and directed during the sample collection process by a trained health care worker at the specimen-collection site.”

Garcetti said paramedic-firefighters are at every testing site, but are not the ones assisting people with the test.

The FDA alert also notes that a person who incorrectly receives a negative result will be delayed in receiving treatment, and efforts to trace others who may have been exposed to the person will also be delayed, potentially resulting in further spread of the virus.

Garcetti said the city will “double down” on education to make sure test takers at the city’s sites know how to properly take the test.

Curative issued a statement this week defending its test.

“Curative’s test has been validated and is being offered during the pandemic under an Emergency Use Authorization, and is labeled with specific warnings, precautions and limitations that FDA reiterated in the safety communication,” according to a statement from the company.

“The test performance and labeling, however, have not changed, nor has the company observed any changes in test performance. We have been working with the agency to address their concerns and these limitations, and we will continue to work interactively with FDA through the Emergency Use Authorization.”

Company officials said they remain committed to following all federal regulations and to ensuring its tests “meet or exceed our customers’ expectations.”

County health officials have long warned against over-reliance on a negative test result, saying that anyone who believes they were exposed to the virus should quarantine themselves, even if they tested negative. The county’s website notes that a negative test only indicates the virus wasn’t detected at the time the sample was taken, adding that a negative results “can also happen if the test was taken too early or the test missed your infection.”

The county’s testing website also states that “no test for COVID-19 is perfect” and could result in false negative or positive results.

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