Do serology tests make sense for Vermont?

Published: Jun. 15, 2020 at 5:42 PM EDT
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While diagnostic tests are a key to monitoring COVID-19 outbreaks, Vermont will not be investing in antibody tests. Our Cat Viglienzoni explains

the health commissioner doesn't think the tests would accurately reflect the spread of the virus here.

"It's a 50-50 coin toss," Vt. Health Commissioner Dr. Mark Levine said.

Monday, Levine told Vermonters not to rely on serology testing to get answers about whether they may have been exposed to COVID-19 over the past four months. Those tests look for COVID-19 antibodies in your blood.

Levine says his working group identified at least four tests that met their standards but the state won't be investing in them.

"We're choosing not to embark on testing the whole state of Vermont right now," he said.

Levine says that's because the serology tests would come back with a high rate of false positives. They believe too few people have been exposed to the virus-- less than 5% of the population-- which makes getting a positive serology test more likely to be wrong than right.

"Which means essentially three out of every four people who get a positive result on the antibody test-- that's a false positive result," the health commissioner explained.

Narrowing in on the recent outbreak in Winooski, only 17% of the people in the outbreak are showing any symptoms, likely because many are children.

I asked if children would be good candidates for focused serology testing given their apparent lack of symptoms. Levine said maybe but they aren't finding high rates of infection in kids.

"It's really hard to know because, again, we don't think kids are spreading it that much amongst themselves and amongst adults," he said.

Back in April, I went to Copley Hospital where staffers there were helping to test the accuracy of one of the early serology tests on the market. I asked Copley's Chief Medical Officer Dr. Donald Dupuis what he thought of the test.

"Probably not ready for prime time," he said.

Dupuis says they while their tests for long-term antibodies showed some promise, others had too many false positives. He thinks the test may have picked up a different coronavirus. He says there were conversations among hospitals in the state about using serology testing but they decided to hold off until the tests were more refined.

"It's one thing for the test to work OK in the laboratory, it's another thing for it to work OK once you let it go," he said.

You can ask your doctor for an antibody test if you want it but they may not order one given the likelihood of a false-positive result. However, the state's working group did leave open the idea that Vermont could do population-level serology testing as part of national or university-based studies.