Critter Corner: Why Should I Consider Antibody Testing for COVID-19?

Dear Oakley,

I’m pretty sure I had a mild case of COVID-19 earlier in the year. Do you think I should go and get an antibody test, and if so, why? What is the difference between an antibody and an antigen test? Is antibody testing covered by Medicare?

Thanks for your help!

Anne T. Boddie

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Dear Anne,

If you have been following the news about research into COVID-19 treatments, you may have seen mentions of antibody testing. Many people are seeking more information about what antibody tests actually are, how they differ from similar-seeming tests — such as antigen tests — and if they are of any use.

Antibody Tests vs. Antigen Tests

Antibody testing involves screening a sample of blood for tiny molecules called antibodies that have “learned” to respond to a particular pathogen, such as a virus.

Antibodies recognize and fight off specific viruses through exposure to them. This means that if a doctor finds antibodies that respond to a certain virus in a person’s blood, they can confirm that the person has overcome an infection of that virus.

By contrast, antigen tests, which typically rely on swabs from the nose or throat, show whether the person currently has the viral infection. The presence of antigens in a sample indicates that the virus is also present and active — and therefore infectious.

Advantages of Antibody Testing

Some researchers argue that deploying antibody tests more widely in communities could help ease the restrictions put in place to slow the spread of the coronavirus. A better understanding of how many people have recovered from COVID-19 and how many people have antibodies to it would enable specialists to more accurately estimate the dynamic and rate of the virus’ spread.

Antibody tests could also play an additional role — confirming who qualifies to donate convalescent plasma, a component of blood that contains antibodies. Currently, researchers across the U.S. are testing the use of convalescent plasma therapy in the treatment of COVID-19. This therapy involves transfusing people who have COVID-19 with plasma from people who have already recovered from the disease and who have formed antibodies to the virus. The transfusion could help the body fight off the infection.

Disadvantages to Immunity Testing

Researchers fear that people who assume that they are immune to a second infection because they have received a positive test result may ignore public health advice. This could increase the risks of continued transmission.

Are Antibody Tests Available?

In light of the potential benefits of antibody testing, researchers affiliated with various healthcare and pharmaceutical companies have rushed to develop accurate tests that could be distributed through healthcare professionals and, eventually, to people’s homes.

Abbott, a pharmaceutical company, claims that their test has “99.6% specificity and 100% sensitivity for patients tested 14 days after symptoms began,” which would indicate a very high level of accuracy. Similar claims have come from Roche, another pharmaceutical company, about their antibody test, which has also received FDA emergency use authorization.

For people in the U.S. who wish to take advantage of antibody tests, the Centers for Disease Control and Prevention (CDC) encourage them to contact their healthcare providers for more information.

Keep in mind that Medicare covers COVID-19 tests, COVID-19 monoclonal antibody treatments, and COVID-19 vaccines.

Hope this helps. Stay safe and hhealthy out there!

Oakley