Q & A: Antibody Test

Your Questions Answered

COVID-19 Antibody Testing


Q: What is SARS-CoV-2?

A:   SARS-CoV-2 stands for Severe Acute Respiratory Syndrome Coronavirus Type 2, the virus currently causing the COVID-19 pandemic.


Q: What is the antibody test?  

A: The antibody test detects whether a patient has any evidence of a previous COVID-19 infection. The test consists of obtaining a blood draw from the patient and then testing the blood to determine its antibody response to the infection. Antibodies develop when the immune system responds to a germ, usually a virus or a bacterium. With other diseases, the IgG antibody usually develops within three to four weeks after infection and lasts for a long time. After you develop IgG antibodies, your immune system recognizes the cause of the antibody formation and can fight it the next time you are exposed. The COVID-19 virus appears to result in the body producing IgG antibodies, however, it is unclear exactly when then antibodies are formed and whether everyone infected forms the antibodies. The antibody test should not be confused with the nasal swab PCR test, which detects the actual COVID-19 virus and indicates an active infection.


Q: Who is a good candidate for the antibody test?

A: A typical candidate for the antibody test has no current symptoms although they may suspect they had a prior infection or have had some symptoms in the past.


Q: What is the process for getting the antibody test?

A: Patients may visit a clinician who will provide a medical evaluation of your current and past symptoms to determine whether the test is appropriate for you. If you are a candidate, the test consists of a blood sample taken during your visit. However, the clinician may choose not to conduct the test due to the possibility of false positives or negatives.


Q: How long does it take to receive antibody test results? 

A:   Test results are usually available within 48 hours, and some patients receive results in as few as 24 hours. Test results will be shared with you via either a phone call from one of our representatives or will be posted to your personal lab account website.


Q: What results are reported for the antibody test?

A: The results for this test are reported as “reactive,” “nonreactive,” or “indeterminate.”

  • Reactive: This result indicates that IgG antibodies to the virus were present in your blood specimen. A reactive result can mean you were infected with the virus in the past or that you are currently infected. If you have not already tested positive for coronavirus, another test may be needed to determine whether you are currently infected.
  • Nonreactive: This result means that IgG antibodies to the virus were not present in the blood; however, you may still be infected. A PCR test may be performed to determine whether you are currently infected.
  • Indeterminate: An indeterminate result means that the test did not produce a clear result for either nonreactive or reactive. This could be the case if the test reacted with other antibodies in the blood or if you have coronavirus antibodies but at levels too low to be reported as reactive.

Q:  I tested reactive (positive) for the antibody test, what should I do?

A: A positive antibody test indicates that you were infected with COVID-19 in the past and that your immune system developed antibodies that can try to fight it off. This can also identify people who had an infection in the past, even if they showed no symptoms of the illness. A reactive result may help determine a level of COVID-19 immunity. This may also be helpful knowledge if a decision must be made as to who could safely work in certain jobs. In some cases, it could also help determine when the COVID-19 illness occurred and who may qualify to donate convalescent plasma (a blood product that contains antibodies against COVID-19 and can be used as a COVID-19 treatment). If large numbers of people take the test in a community, public health leaders and researchers can determine what percentage of the population has already experienced COVID-19.


Q:  If I test positive to the antibody test am I immune to COVID-19?

A: The antibody test detects whether you have had a prior infection of COVID-19. However, because this virus is so new, we are still learning about it, and we cannot say with certainty that any developed antibodies will equate to immunity and/or what the duration of the immunity may be. As a result, even if you have antibodies, you should continue to practice social distancing and wear masks in public.


Q:  How much does the test cost?

A: Patients should check with their medical insurers to determine whether the tests are covered under your insurance plan. If you do not have insurance, the general cost of the antibody test and PCR ranges from $50 to $100.


More details on interpreting COVID-19 Test Results, please click here.


Dr. Joe Chow, President, TeamHealth Ambulatory Care
Dr. Shyamal Majithia, Medical Director, WNY Immediate Care
Texas Department of Health State and Health Resources, COVID-19 Testing: PCR Versus Serology Testing, Explained Version 1.0. Released 4/20/2020.