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Wellness
What does a COVID-19 antibody test really tell you?
Before you rush to a lab to get your immunity to the virus checked, here's what you need to know
Now that India is a few months into the coronavirus outbreak, conversation about taking COVID-19 antibody tests to test your status is getting more common. The WHO is considering it to be a badge of immunity for now, but what are they, and are they completely accurate? With private labs across India offering antibody testing for anyone who wants it, knowing the details before high-tailing it to the nearest lab is important. We spoke to Dr Behram Pardiwala, internal medicine expert, Wockhardt Hospital and Dr Laxman Jessani, consultant, infectious diseases, Apollo Hospitals, Navi Mumbai for their take.
What is antibody testing?
“When you have an infection, the bug is called an antigen. To fight this antigen, the body makes antibodies which are proteins, causing an immune response to the infection. There are three types of antibodies present in the body, of which, those which react immediately after the antigen has been detected are called IgM [immunoglobulin] antibodies. Long term immunity results in IgG antibodies,” says Pardiwala. These provide some protection from getting the disease again, or an improved means of fighting it.
Another, more promising alternative that may be gaining speed? Antigen testing. “It looks for specific proteins found in the virus,” says Dr Jessani “It’s a reliable test that will detect the presence of the virus in the body by directly identifying the genetic material and the infection," he says.
Antibody tests can tell you if you've been exposed to the virus
For those taking an antibody test, doctors are looking to see if the person has been exposed to the COVID-19 virus in the past. If you test positive for those antibodies a month or more after you were exposed, it suggests that you probably did have COVID-19 in the past.
Antibody tests have always been used to check if the body has developed an immune response and resistance to diseases such as Hepatitis B post-vaccination. “Vaccines are developed with this principle. Vaccinations give a small amount of virus into the body of the person which will not cause the disease but set an immune response. Once the antibodies are produced, even when you are exposed to the virus, you won’t develop the infection as the antibodies are fighting the infection,” says Dr Jessani.
However, they can't tell you if you're immune forever
There is conflicting research about building immunity to the virus in the long term. Some experts say that having antibodies may provide some protection against getting it again, but does not prove that having it once can be a stopgap to ever contracting it again.
They can help track the spread of the virus
With many asymptomatic COVID-19 patients getting out of the strict lockdown, the antibody test may now prove crucial to check how many people may have been exposed to the virus while they were unaware. “Antibody tests are more useful for surveillance (to understand the immune response and status of the community) and is not to be used as a diagnostic tool," says Dr Pardiwala.
They can be used to test for plasma therapy
"Antibody tests are also being done for experimental convalescent plasma therapy where the antibodies of those who have recovered from COVID-19 are transferred to help fight the virus and provide protection to the recipient,” Dr Jessani sums up.
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