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As the SARS-CoV-2 pandemic continues with global cases nearing 2.5 million, clinicians have raised questions about the accuracy of available COVID-19 tests. After in-house testing of different available tests, one physician found that Abbott’s assay using its ID NOW device, which can provide results in 5–13 minutes, has a false-negative rate that nears 15 percent. The full results, first reported by NPR, have not been published or peer-reviewed.

Gary Procop is the chairman of the commission of science, technology and policy for the American Society for Clinical Pathology, and is currently heading up COVID-19 testing at Cleveland Clinic. He and his team took 239 patient samples known to be positive for the virus and re-tested them using five products available through the US Food and Drug Administration’s (FDA) emergency use authorization. The test that turned out to be the least accurate is the one known for its speed.

The ID NOW machine was granted emergency use approval during the pandemic on March 27 and generated buzz after President Donald Trump unveiled it during a press conference. In Procop’s analysis, Abbott’s test had a false-negative rate of 14.8 percent.

“So that means if you had 100 patients that were positive, 15 percent of those patients would be falsely called negative. They’d be told that they’re negative for COVID when they’re really positive. That’s not too good,” Procop tells NPR, adding that, ideally, test reliability should be above 95 percent.

The DiaSorin Simplexa test had a false-negative rate of around 11 percent. Tests developed by the US Centers for Disease Control and Prevention, Cepheid, and Roche had false-negative rates of 0, 1.8, and 3.5 percent, respectively.

In the wake of the study’s results, Procop’s facility is no longer using the Abbott test, and he is not the only administrator to make that decision.

Alan Wells, a pathologist at the University of Pittsburgh Medical Center, tells STAT that his facility is not using the test anymore because the viral load of the patient might play a role with testing accuracy, more readily identifying those with higher levels. “However, with lower loads of virus, a large fraction of these patients were not detected as positive,” he says.

STAT also reports that Emily Miller, an OB-GYN at Northwestern University, referred to the test as “clinically not useful” to identify the virus in expectant mothers.

According to NPR, Abbott disagrees with Procop’s findings, stating that any errors might come from the use of viral transport media, which is commonplace in testing and helps extend the shelf life of the sample. All of the samples in Procop’s study used this media rather than testing directly from the nasal swab. Abbott has sent letters to the healthcare facilities that have received some of the 600,000 tests, advising them to test directly with the swab, which yields the most reliable results.

Because the FDA cleared the test for use directly with the swabs as well as with transport media, Procop tells NPR that he wants additional clarification on the accuracy of the test, because of the more significant implications of false-negative results.

Due to the nature of this novel coronavirus, manufacturers have had to scramble to not only develop tests capable of detecting the virus but also mass produce them and get them into the hands of frontline healthcare workers quickly. The urgency of the situation has also caused the FDA to grant the tests approval under emergency use authorization, which foregoes much of the rigorous testing that would ordinarily be required.

“It is a risk that if you tell somebody they’re negative and they’re truly positive that they will relax social distancing, not wear a face mask, etc., and could transmit the disease,” Procop tells NPR. “If you get back a negative test and think, ‘I don’t have it and I can go to a mixer,’ and now everybody at the mixer has now been exposed to you.”

Additionally, Procop explains, patients admitted to the hospital for unrelated reasons might still be carrying the virus. If they are incorrectly determined not to have the virus, they could pose a risk to other patients in non-COVID wings, furthering the spread of the virus.