Chicago Health Officials Using Antibody Testing to Determine if Someone Had the Virus

The city’s Department of Health has begun administering a limited number of antibody tests to determine whether an individual has contracted COVID-19, Health Commissioner Allison Arwady reported Saturday morning.

The so-called serology tests use a blood sample to detect antibodies to the virus rather than the virus itself. Such tests, the first of which received emergency FDA approval earlier this month, are different than the nasal swab tests that have been used to determine whether an individual actively has COVID-19.

The antibody tests, which determine whether an individual previously contracted the coronavirus and is likely to be immune currently, are viewed as crucial in understanding the risks to the country’s population moving forward.

If an individual tests positive for the antibodies, which are likely to show up within two to six weeks of infection, health officials believe they’re not going to get sick or spread the virus, because their bodies are killing it off.

As elected officials have searched for ways to jumpstart the nation’s economy, some have suggested those with antibodies could leave self-isolation and return to work sooner than those who have yet to contract the coronavirus.

For now, Arwady said the testing is in its infancy, and she cautioned the city is using it in conjunction with the nasal tests to get a feel for the serology test’s accuracy. She noted that the antibody tests currently have a higher rate of false negative and false positive results.

“We’ve just added a little bit of that antibody testing, trying it ourselves, but only in conjunction with … the nose one, because that’s the one that is truly in place for clinical diagnosis,” Arwady said Saturday morning during her daily question-and-answer session online. “We want to have a good understanding of how these tests, as they develop, really function in the world, because that’s such an important thing.”

Arwady did not say how many of the tests the city currently is administering. She predicted such testing would become more widely available in the coming weeks and months and said to expect more approvals of such tests from the Food and Drug Administration soon.

“I think we will eventually have very widespread antibody testing. I think we’re going to need it. It’s how we’re going to understand, as a city and as a country and as a world, where we are in terms of coronavirus. We’ll be using it probably around shelter in place, but it’s just still early,” Arwady said.

“It’s coming really soon. I think we’ll see FDA announcements probably in a matter of a few weeks. I would guess maybe even shorter, but then it’s about as the tests are getting approved, they still will have caveats around them.”

Arwady said there will be a trial-and-error phase and health officials determine the accuracy of the tests, many of which are being rushed through the approval process.

“They’re really best used for population surveillance. We’re excited about them,” she said. “We’re excited about obviously being able to use them, but you have to pair them with the ones that are approved to make sure you’re not giving people false negatives and false positives and making all kinds of assumptions.”