What Antibody Tests Don't Tell Us

Published: May. 21, 2020 at 2:26 AM CDT
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Minnesota health leaders say one COVID-19 test may not hold the answers you expect.

A month ago, Gov. Tim Walz announced a “Minnesota Moonshot: A system that would test up to 20,000 people a day for COVID-19, and another 15,000 for antibodies.

But the highest so far has been 8,600 viral tests, and some doctors question the practical usefulness of the current antibody tests.

Chris Villegas of Minneapolis and Julia Nemes of Shoreview both want a serology test to see if they’ve been exposed to COVID-19 and have the antibodies.

“I could potentially have contracted it at some point and created antibodies myself,” Villegas said.

Nemes believes she may already have had the virus.

“My husband and I were both sick the last week in February, first two weeks in March,” Nemes said,

And they’re not alone. But Park Nicollet’s Dr. Mark Sannes, who specializes in infectious diseases, says current tests do not reveal much practical information.

“It doesn’t tell a person if they have immunity to COVID-19,” Sannes said.

Jan Malcolm, commissioner of the Minnesota Department of Health, is also cautious.

“The evidence is still very much out on what serology tests tell us or don’t tell us, such that it’s not thought to be really useful information,” Malcom said.

Kris Ehresmann, the MDH’s infectious disease director, echoes her collegue.

“There are still so many things unknown that we’re not actively promoting this for individuals,” Ehresmann said.

For many, the test is about peace of mind. Nemes just wants answers, and Villegas believes the more data available, the better.

But Dr. Sannes warns even results from FDA-approved serology tests are shaky.

“A positive test is really difficult to interpret. You know, in the best of scenarios, about one in three of those positive results will be falsely positive,” Sannes said.

He says a good candidate for the test would be a hospitalized patient who doctors have been unable to diagnose. But employers, for instance, would not be able to use serology testing to “clear” their workforce to return.

“It’s not a test that should tell you this is a group that I don’t need to worry about,” Sannes said.

For now, serology testing would help collect data, but wouldn’t unlock practical information.

“There may be instances where it’s useful, but there aren’t very many of them right now,” Sannes said.

A serology test needs to be ordered by a doctor. If you are doing one, the state recommends finding an FDA-approved test.

HealthPartners and Park Nicollet have ordered fewer than 10 COVID-19 serology tests.

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