It is very sensitive (>90%), meaning that it will usually detect antibodies if they are present. It is also very specific (>99%), meaning that it will be negative if antibodies are not present.
Although this is a good test, it is possible to have a “false positive” result due to the low number of people with COVID-19 in the community. This means the test could be positive even if you were never infected. This is true for all antibody tests when the number of infections in the community is low. Antibody tests from some manufacturers will test “positive” if a person has had a previous infection due to coronavirus that causes routine colds in addition to the virus that causes COVID-19.
Accuracy of antibody tests made by different manufacturers are not equivalent. You should talk with your health care provider about the test his/her laboratory uses before being tested.
No. The antibody test is not used to diagnose acute infections. Antibodies do not develop until days to weeks after infection. If you have any concerning symptoms for COVID-19 (fever, shortness of breath, cough, muscle pain, sore throat, loss of taste or smell, or new diarrhea), you should talk to your provider about getting a different test that looks for the virus itself.
We do not know yet if a positive test result means that you are immune, and if it does, for how long immunity might last. We hope to learn more about these questions with research studies such as the COVID-19 Community Research Partnership.
If your test is positive, you should continue to follow CDC and local public health recommendations on social distancing, hand washing and mask use; and quarantine as directed by public health if you have been in contact with a person known to have COVID-19.