Q & A: Antibody Testing

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 a patient develops IgG antibodies, their immune system recognizes the cause of the antibody formation and can try to fight it the next time the patient is 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. It’s thought that IgG for COVID-19 should be detectable by 10-14 days after the start of an infection. 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.  If a person has had symptoms as recently as two weeks ago, it may be too early for the antibody test to be accurate and the test may be falsely negative.


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

A: Patients may visit a clinician who will provide a medical evaluation of their current and past symptoms to determine whether the test is appropriate. If the patient is a candidate, the test consists of a blood sample taken during the 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-  Test results will be shared by phone call from one of our representatives.


Q: What results are reported for the antibody test?

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

  • Reactive (Positive): This result indicates that IgG antibodies to the virus were present in the blood specimen. A reactive result can mean the patient was infected with the virus in the past or that they are currently infected. If the patient has not already tested positive for an active infection with coronavirus, another test may be needed to determine whether they are currently infected. Please note that a past infection with a different coronavirus may also result in a reactive/positive test. At this time testing can’t tell the difference between the different human coronaviruses.
  • Nonreactive (Negative): This result means that IgG antibodies to the virus were not present in the blood; however, the patient may still be actively infected. A PCR test may be performed to determine whether the patient is 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 the patient has 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 the patient was infected with COVID-19 in the past and that their 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. In the future, a reactive result may help determine a level of COVID-19 immunity. That determination can’t be made at this time. 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 the patient 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 the patient has antibodies, they 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 their insurance plan. If the patient does not have insurance, the general cost of the antibody test and PCR ranges from $50 to $100.



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.