Coronavirus California

COVID-19 testing is important but has 10 to 15% rate of producing false, negative results, pathologist says

ByDavid Louie KGO logo

Friday, March 27, 2020

Coronavirus testing is vital but not perfect, health expert says

The rollout of COVID-19 testing is accelerating as more kits become available. However, a leading pathologist who was director of virology at Stanford, points out that the results are not 100% accurate.

SAN CARLOS, Calif. (KGO) -- The rollout of COVID-19 testing is accelerating as more kits become available. However, a leading pathologist who was director of virology at Stanford, points out that the results are not 100% accurate.

"It's not that these tests can't detect virus," said Dr. Bruce Patterson. "My concern is that the sampling involved in detecting the virus can lead to clinical false negatives."

Patterson says he expects the rate of false negatives to be 10 to 15% in line with testing for other viruses, including seasonal flu.

"Are they positive when you have the disease or are they positive or negative when you don't have the disease?" Dr. Patterson asked. "Those are the clinical performance metrics that physicians rely on with every test that we do."

Patterson is the CEO of IncellDx, which is running samples of COVID-19 at the company's San Carlos labs. His research and development are focused on treatments for patients with HIV and cancer who have at risk for the coronavirus.

You've probably heard White House task force member Dr. Anthony Fauci underscore the need for more testing. Current COVID-19 testing is being done with nasal swabs. However, Dr. Patterson says pathologists learned 17 years ago during the SARS epidemic that throat swabs provided better data.

"We were surprised by the fact oralpharngeal swabs had a higher viral load than the nasopharyngeal swaps which, of course, contributes to sensitivity for detection," he said.

Doing a throat swab is more invasive and more time consuming compared to drive-by testing.

With pressure to get people back to work, Dr. Patterson believes blood tests to detect individuals who have developed antibodies to COVID-19 could be a key step. They would have protection.

In the meantime, IncellDx is expecting results soon from a treatment it has been working on with a partner.

"We're thinking like chess players, four moves ahead... to say, what is the next wave of diagnostics that will be critical in defeating this pandemic," he said.

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