COVID-19 antibody test plays big role in learning more about the disease

Posted at 12:59 PM, Apr 21, 2020

Dr. Elitza Theel is the Laboratory Director for the Infectious Diseases Serology Lab at the Mayo Clinic , which is one of many medical centers across the U.S. that has started to roll out a COVID-19 antibody test.

“It’s a new virus, it’s a fairly new test for the virus, so there’s a lot to learn,” Dr. Theel said.

SARS-CoV-2 is the virus that causes the COVID-19 disease. Dr. Theel says antibodies are produced by our immune system in response to an infection.

“I guess you can think of them as small molecules or proteins – so these antibodies that our immune system produces will bind to the SARS-CoV-2 virus, and they will basically inactivate and kill it,” Dr. Theel said.

The Mayo Clinic made its antibody test available two weeks ago.

“We’re restricting use to individuals for whom COVID-19 has been either diagnosed or at least highly suspected and they’re at least 11 days post onset."

According to Dr. Theel, it takes time for antibodies to develop – anywhere from a week to two weeks after initial infection. Microbiologists don’t know yet if the presence of antibodies means you’re protected from future infection. However, it’s certainly possible and the number of antibodies in your system could make a difference. That’s why Mount Sinai Health System in New York has created what it calls a semi-quantitative test.

“I can’t tell you the exact amount, but I can tell you if there is a little bit of antibody, somewhere in the middle, or something very high,” Dr. Jeffrey Jhang said.

Dr. Jhang is the Medical Director of Center for Clinical Laboratories with Mount Sinai Health System. He says there are multiple reasons an antibody test – also known as a serologic test – can be helpful. For one, plasma can be extracted from a patient who has recovered from COVID-19 to treat patients who are currently sick. Plasma is the fluid that carries blood components like red and white blood cells throughout the body, and it contains antibodies.

“We’ve collected over 200 units of plasma from recovered donors and treated over 50 patients with that plasma,” Dr. Jhang said.

The test can also be helpful in finding those who may have been a-symptomatically infected – meaning they caught the virus and could spread it, but never showed any symptoms.

“Certainly I have encountered people who have said ‘I didn’t have any symptoms at all, well ya know, if I think about it, maybe I had a little bit of a cough’ and then they do have the antibody,” Dr. Jhang said.

There could be many people out there in similar situations which would mean more people have antibodies than we even realize. Having a serologic test widely available would help doctors know if that’s truly the case.

“Over time, we can see if as a population we reach some sort of herd immunity status. In which case, a majority of the population would have these antibodies and we would expect there would be fewer new cases of infection,” Dr. Theel said.

Since the virus has only been active about four to five months, both Dr. Theel and Dr. Jhang say we need more time to discover the true effectiveness of these antibodies.

“We really need to determine whether those antibodies are related to protection, and how long does that protection last,” Dr. Jhang said.

In the meantime, both labs are working to create as many tests as they can, sharing their information with other clinical laboratories so the test can hopefully be distributed nationally in the future. Dr. Theel says it could play a role in determining when everyone can go back to work.

"I don’t know that it’s the silver bullet. I don’t know that we are really going to be able to say based on a serologic test alone that this group can go back to work and this group cannot. I think it might be a factor in that, but I don’t think it should be the only thing we base those decisions off of,” Dr. Theel said.