FDA clears assumptions surrounding COVID-19 antibody tests’ accuracy

FDA clears assumptions surrounding COVID-19 antibody tests accuracy

The U.S. Food and Drug Administration (FDA) defended the reliability of COVID-19 antibody tests, saying that false results only recognize the tests’ “inherent limitations.”

While most states and businesses believe that the implementation of mass COVID-19 antibody tests is key to reopening the economy, health experts warned that such massive testing might come unreliable.

Gottlieb: ‘I wouldn’t put confidence in any one test’

On Monday, May 4, Dr. Scott Gottlieb discussed in his recent talk with CNBC’sSquawk Box” that the COVID-19 antibody tests have a high probability of yielding false results.

The former FDA commissioner shared that one test is not enough, suggesting that people should repeat it twice or thrice. He also adds: “I know they’re expensive, but I wouldn’t put confidence in any one test.”

FDA clears assumptions surrounding COVID-19 antibody tests accuracy

CEO Severin Schwan of pharmaceutical company Roche echoed the same sentiment as well, calling some coronavirus antibody tests a “disaster.” He also adds that the tests have “very little use.”

The test’s high percentage of false-positive raised Gottlieb’s concerns over false security the results could instill to people. According to him, it could make a person “reasonably confident” that he has antibodies

The catch is that it is still unverified how long antibodies last — whether it is months, years, or more.

FDA says antibody test loophole is its ‘inherent limitation’

The FDA, in its revised policy on antibody tests published on Monday, has cleared the assumptions surrounding the antibody tests’ reliability.

The federal agency explained that even high-quality test kits produce false results and may vary depending on the number of infected persons in a population.

For instance, if the coronavirus antibody test is used on people in an area where the infection rate is low, the test will likely produce more false-negative results because finding someone who contracted the virus is small.

However, the institution notes, it does not mean “it is unreliable.” They added:

“It rather recognizes the inherent limitations of these kinds of tests. Thus, it may be necessary for some to have two serology tests performed to generate reliable results.”

COVID-19 antibody tests also yield correct results, if not always. In a study conducted by the University of California, researchers used and compared 10 serological samples to see its accuracy. The test’s sensitivity hit the 90% mark.

The authors also noted that most kits were 95% to 99% specific, which implies that its false-positive rate is under 5% only.

How accurate are COVID-19 antibody tests?

According to The Conversation, there are two factors to distinguish a test’s accuracy: specificity and sensitivity.

A test measured by specificity can precisely identify people without the virus, which means it recognizes true negatives.

Test by sensitivity, on the one hand, can identify those who contracted the coronavirus and yields correct positive results.

Both aspects measure a serological test or an antibody test. There is, however, a loophole that FDA describes as “inherent limitations.”

Here’s how:

  • If the result of the test is 90% sensitive, it will detect the same percentage of people who contracted the virus. However, the remaining 10% who are infected will be identified as a false negative.
  • If the test is 90% specific, 90% of people who are coronavirus-free will be recognized as true negative. But the remaining 10% will be registered as positive even though they are negative (false positive).

FDA set strict standards for antibody test manufacturers

The FDA has henceforth ordered all antibody test manufacturers to submit authorization forms as well as data supporting that their test kits work.

The decision was made following a lack of test validity and possible fraud.

The agency is also looking to provide “performance threshold” recommendations to developers to ensure the test kits’ quality.

All providers were given a 10-day timeframe to submit all requirements. Otherwise, they will face removal.

As of this writing, the FDA has approved 12 coronavirus antibody test for emergency use, with 250 tests still waiting for EUA review and approval,  according to FDA Commissioner Stephen Hahn.

Images courtesy of The National Guard/Flickr, Jarmoluk/Pixabay

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