Medical experts are reportedly worried that close to 33% of people who should test positive for the coronavirus are not and don't realize they're infected

Claudio Furlan/LaPresse via AP

• Different coronavirus tests can have different rates of false negatives, experts told The Wall Street Journal.
• If a patient tests negative but later develops more symptoms, they could be unknowingly spreading the virus.
• The FDA has approved 20 testing providers so far as officials race to accelerate testing across the country.
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With many tests for the novel coronavirus being developed at a caffeinated pace, some medical experts are warning that they could have wildly different accuracy rates.

Doctors told The Wall Street Journal that the US Food and Drug Administration's "unprecedented flexibility" for test developers — which has so far authorized 20 tests — leaves some providers lacking total confidence in their efficacy.

"The whole testing field is in flux," Bill Miller, a physician and epidemiologist at the Ohio State University, told the paper. "The thing that is different this time is most of these tests are going through a really rapid validation process. As a result we can't be completely confident in how they will perform."

In some cases, in Texas and New York, patients tested negative but later came back to the hospital with covid-like symptoms and eventually tested positive. One doctor, Mike Lozano of Envision Healthcare, estimates close to 33% of people who should test positive for the coronavirus are not and don't realize they're infected, he told the paper.

Typically, the Centers for Disease Control and Prevention studies a test's accuracy, a former CDC statistician told The Wall Street Journal, but that can take a year. Officials across the country have called for accelerated testing to "flatten the curve" and prevent hospitals from being overrun with critically ill patients. On March 28, the FDA approved a test from Abbott that delivers positive results in five minutes and negative results in 13 minutes.

Meanwhile, companies are also ramping up development of tests to determine if recovered patients possess antibodies that may be used to treat others with the virus.

"It's critical that the tests used work," the FDA said. "False results can also contribute to the spread of COVID-19. We want our treatments to be tested for effectiveness and reviewed by the FDA. We want the same for our tests—assurances that they are accurate and effective."

Correction: An earlier version of this article incorrectly stated that close to 33% of people testing negative for the coronavirus may be infected. This is not true. Rather, experts are concerned that close to 33% of people who should test positive are not. This article has been updated and we apologize for the error.

Paulina Cachero contributed reporting

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