In the midst of the COVID pandemic, many are wondering, “Have I been exposed to COVID? Or maybe I had a mild case?” Antibody testing may be able to answer those question and is rapidly becoming available throughout Maryland.
Antibody Test vs Viral Test
There are primarily 2 tests for COVID.
One test, which is a nose or mouth swab, is used to determine if someone who is currently sick has the virus that causes COVID.
The 2nd test is a blood test looking for antibodies to COVID. This test can tell whether someone has been previously infected with COVID.
COVID Antibody Testing
Antibody testing (also called serology testing) looks to see if you have developed antibodies, the proteins critical for fighting off and clearing out the virus that causes COVID-19.
It is very important to wait a minimum of 14-20 days from the time of sickness or exposure to COVID before having the test. It takes your body at least 14 days to make the antibodies found in the test.
All COVID Antibody Tests are not Created Equally
In the US currently, there are over 200 different lab tests for COVID antibodies. One professor of immunobiology said “It’s kind of like the Wild West.”
“Some of the antibody tests had absolutely unacceptable false positive or false negative rates,” Dr. Michael Freedman of Evolve stated.
Dr. Freedman went on to say, “Small differences in sensitivity and specificity are everything here. One test which was approved with 93.8 and 96.0% has only a 55% positive predictive value if 5% of the community has had COVID. That’s not much better than a coin flip!”
“The test we are using is with Abbott Architect and was approved by the FDA
Monday. Their data is showing 100% sensitivity and 99.6% specificity which gives it a positive predictive value of 97% and 100% negative predictive value in a population with 5% prevalence,” Dr. Freedman added.
Positive predictive value means that if you get a positive test, you really do have the antibodies. Negative predictive value means that if you test negative, you really don’t have the antibodies. Scientific American recently published an excellent review of this information.
What does a positive COVID antibody test mean?
A positive result means you were exposed to COVID-19. But it does NOT mean you are immune to COVID-19.
Even if you are immune now, we don’t know how long that immunity will last.
A study of SARS, which is another coronavirus, found only 25% had antibodies after 3 years. After 6 years, almost no one still had antibodies.
Another study looking at people who had MERS (another coronavirus illness) showed only people who got very sick had antibodies after 2 years but people who had mild illness did not.
Therefore, experts say following social distancing and proper hygiene is just as important as it was before you got the test.
What does a negative COVID antibody test mean?
A negative test result could be because:
- You have not had COVID-19 or
- Your immune system has not produced the antibodies to the virus yet, or perhaps isn’t able to produce antibodies.
The Bottom Line
Currently there are no recommended changes in your day to day life that would occur based on the COVID-19 antibody test results.
The World Health Organization has specifically warned, “At this point in the pandemic, there is not enough evidence about the effectiveness of antibody-mediated immunity to guarantee the accuracy of an “immunity passport” or “risk-free certificate.”
Whether your result is positive or negative, experts strongly recommend people continue to strictly follow all recommendations for preventing the spread of this virus.
If you become ill with symptoms that are consistent with COVID-19 you should immediately consult a medical provider to determine if testing for an active infection is recommended even if your antibody test was positive. For more information, about Coronavirus (COVID), click here.
If you have been experiencing fever, headache, dry cough or any of the above symptoms, please CALL your doctor immediately.