COVID-19 antibody tests look for proteins in your body that your immune system has produced to fight an infection from SARS-CoV-2, or COVID-19. If you receive a negative test result, you have most likely not been infected by COVID-19. However, it is possible to receive a false-positive test result for COVID-19. Make sure to keep the following considerations in mind when interpreting a negative antibody test result.
The CDC reports that individuals start producing antibodies one to three weeks after being infected by COVID-19. Therefore, if you have an active infection or are tested too soon after becoming infected, you could still receive a negative test result as your body isn’t yet producing antibodies.
Most blood antibody tests available today look for IgG or IgM proteins, or both. IgG and IgM proteins are found to emerge nearly simultaneously.
Scientists don’t know exactly how long it takes COVID-19 antibodies to fade, but most estimate that they are detectable for at least several months. Studies have found that IgM antibodies decay more quickly while IgG proteins have been detected in the body several months after infection. Since decay is known to occur, it is possible for a person to test negative for antibodies if he or she is tested long enough after infection, or if their body did not produce sufficient antibodies to be detected.
As COVID-19 is still a new disease, much more testing is needed to determine the long-lasting effects of antibodies and immunity to COVID-19. Even when antibodies are present, scientists don’t know yet how much immunity those individuals have or how long they might be protected. The FDA cautions that persons with antibodies should not assume immunity and should still follow public health recommendations.
While unlikely, it is possible to have a rapid negative test result due to an incorrect test or a lack of antibodies despite a COVID-19 infection. A study in Nature of 61 COVID-19 antibody tests found that the specificity estimates—or how accurate a negative test is—range from 95% to 100%. This means that for most tests, there is a less than five percent chance that a negative test result is incorrect.
If a person is showing symptoms of COVID-19, they should first consult their physician about a diagnostic test, as antibody tests are not useful for diagnosing an active COVID-19 infection. The CDC recommends that an antibody test should be administered no earlier than three weeks after the onset of illness in order to obtain as accurate a result as possible. Since scientists know that at least some antibodies decay over time, the antibody test may become less accurate the more time that has passed since infection. However, the decision is a personal one to be weighed in light of the person’s wellness after infection and other factors. While the antibody test shouldn’t be used to determine immunity, a person may want to learn if antibodies are present in order to donate plasma or to make more informed decisions regarding their health.
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Our on-demand COVID-19 PCR testing services are located in Florida, California, Nevada, and Puerto Rico. With a turn around time of 12 hours on PCR tests, you can rest easy knowing that you will receive accurate results in a timely manner with a trusted and reliable partner. Contact us today to learn more about our testing services and to determine if we can assist you on your healthcare journey.