When your body is infected with a virus, your immune system creates antibodies against that virus. IgG (a specific type of antibody) takes several days to develop, and it can persist after infection has ended. If you have COVID-19 specific antibodies, this suggests that you have been exposed to the virus in the past. This test is performed by collecting blood.
How is it different than a PCR COVID-19 test?
A PCR test is done by a nasal swab and detects whether you have COVID-10 virus in your nose at that moment. You get this type of test if you have symptoms such as dry cough, fever, or shortness of breath. It is not helpful in determining whether or not you have had the virus once your symptoms have resolved. This type of test is covered by insurance if your provider determines it is needed.
What do we know about the antibody test?
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Is it FDA approved? – No, it is not. It has been approved for emergency use, but not yet rigorously tested or FDA approved. This means the results are difficult to interpret because the performance of these tests has not yet been fully evaluated.
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How much does it cost? – At this point insurance is not covering this antibody test because it is not FDA approved. That means it can cost up to $200 out-of-pocket to be tested.
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How soon can I get this test if I think I’ve had COVID-19? – Since this is an IgG test, you should wait at least 10 days after you develop symptoms before seeking testing. That gives your body time to create enough antibodies to be detected by the test.
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How accurate is this test? – Unfortunately, at this time, the majority of antibody tests that are available cannot tell the difference between different types of coronavirus. There are many types of coronavirus that are not COVID-19. These other coronaviruses usually cause cold-like symptoms and they are quite common. At Plateau Pediatrics, 4% of respiratory PCRs were positive for other coronaviruses in the past year. If you have a positive IgG for COVID-19, it might be due to one of these other coronaviruses which you have encountered in the past.
A recent report from the Infectious Diseases Society of America confirmed that, based on best evidence at this time, antibodies tests have not been well validated and are not particularly useful. Locally, the Knox County Health Department addressed antibodies tests by saying that “the antibody tests available today are purely experimental.”
There are also reports of non-medical companies, such as window manufacturers, producing unreliable tests for profit.
Does a positive COVID-19 antibody test mean that you’re immune?
At this time we don’t know. Some viruses change over time so that protection from one year’s version does not provide complete protection in the future. For now, it is still recommended that you continue to socially distance when possible, wash your hands, and wear a mask when necessary -- even if you have had a positive antibody test.
