If you’ve taken a blood antibody test for SARS-CoV-2, then you may be wondering how to interpret your COVID-19 antibody test results. The COVID-19 antibody blood test, also known as serological testing, looks for the presence of antibodies that your immune system produces in response to an infection.
As of November 2020, there are 89 serology tests under Emergency Use Authorization in the United States. Some antibody tests look for IgG proteins, some for IgM, and some combined (IgG/IgM). A study in Nature of 61 combined tests found that the specificity estimates—or how accurate a test is when no COVID-19 antibodies are present—to range from 95% to 100%. Sensitivity estimates—or how accurate a test is when COVID-19 antibodies are present— range from 88% to 100%. This means that for most tests, there is a less than five percent chance that a negative test result is wrong. However, a positive test result can have a higher chance of being false.
The blood test for COVID-19 antibodies is typically performed as a finger prick or vein blood draw and can be performed in a laboratory or as a rapid test at any point-of-care healthcare setting, such as your doctor’s office. Studies show that rapid antibody tests are equally accurate as tests performed in a laboratory.
An antibody test does not look for the presence of active COVID-19 infection in a person. Instead, it indicates if you most likely have had COVID-19 in the past. Instead of giving a test results range, your COVID-19 antibody test will report as positive or negative. A person begins to produce antibodies one to three weeks after infection, and while scientists don’t know exactly how long these last, they are thought to remain in a person’s body for at least several months.
While a positive test result most likely indicates that you have had COVID-19, it is possible to have a false positive result. This could be due to a low number of infections in the population where the test takes place or due to the test detecting a coronavirus other than COVID-19. The chance of a false positive becomes increasingly common in an area where the prevalence of COVID-19 is very low. In general, the false positive rate is more variable while the false-negative rate for COVID-19 antibody tests is low.
While less likely, it is also possible to have a rapid negative test result due to an incorrect result or if the person has contracted COVID-19 too recently to have developed detectable antibodies or too long ago that antibodies are no longer active. While experts don’t know exactly how long natural immunity from COVID-19 lasts, it is believed to protect individuals for several months.
A COVID-19 vaccination will cause a positive antibody test result in some, but not all antibody tests. However, an antibody blood test result cannot be used to determine your level of immunity after receiving the COVID-19 vaccine. Blood antibody tests are not authorized by the FDA to determine your level of immunity since the blood tests search for a specific viral protein target that is introduced by natural infection.
For COVID-19 testing, you can rely on the experts at BioCollections Worldwide. We have worked for over two decades perfecting rapid infectious disease testing as well as other essential tests utilized by doctors and private individuals. As the first lab testing for COVID-19 in the United States, and the first drive-through COVID-19 testing provider in Miami, Florida, we take our responsibility to give fast, accurate, and reliable results seriously.
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.