The COVID-19 Antibody test is a blood test that checks for a type of antibody called immunoglobulin G or M (IgG or IgM) that is the result of past or recent exposure to SARS-CoV-2; this is the virus that causes COVID-19 disease. The human body produces IgG antibodies as part of the immune response to the virus. It usually takes around 10 days to produce enough antibodies to be detected in the blood. However, in some people it may take several weeks.
Test results may help identify if you were previously infected with the virus and can check whether or not your body has produced antibodies. Currently, the FDA supports antibody testing with the following important points:
- Antibody tests can play a critical role in the fight against COVID-19.
- Testing can help identify who may have been infected with SARS-CoV-2 and potentially developed an antibody response.
- Right now, it is unclear whether these individuals may be less susceptible to infection, but in the future, broad use of antibody tests and clinical follow-up will provide more information on this point.
Note: This test can sometimes detect antibodies from other coronaviruses, which can cause a false positive result if you have been previously diagnosed with or exposed to other types of coronaviruses. Additionally, if you test too soon, your body may not have produced enough IgG antibodies to be detected by the test yet, which can lead to a false negative result.
The COVID-19 Antibody test is a laboratory-based qualitative immunoglobulin (IgG or IgM) test. Results from the test can be positive (reactive), negative (non-reactive), or, occasionally, equivocal (borderline). There is no numerical value for this test.
A COVID-19 Antibody Test (or SARS-CoV-2 [COVID-19] IgG or IgM test) is used after an individual has already tested positive for a COVID-19 infection or has been infected with the SARS-CoV-2 virus. This blood test examines if an individual has developed antibodies to the SARS-CoV-2 virus, a process which only occurs following an infection with a virus.
A COVID-19 Active Infection test (or SARS-CoV-2 RNA [COVID-19] Qualitative NAAT test) is used to diagnose a COVID-19 active infection when an individual is experiencing symptoms of the COVID-19 disease or has been infected by someone who has been diagnosed with COVID-19. This nasal swab test checks for viral RNA (genetic material) and detects an active infection.
This test may be helpful if you:
- Had a prior positive test for COVID-19 and it has been at least 10 days since you were tested, and you want to know if you have detectable levels of IgG antibodies
- Have not had a fever or felt feverish in the last 3 days
- Have not had new or worsening symptoms of COVID-19 in the past 10 days: loss of smell or taste, shortness of breath or difficulty breathing, feeling weak or lethargic, lightheadedness or dizziness, vomiting or diarrhea, slurred speech, and/or seizures
This test can sometimes detect antibodies from other related coronaviruses, which can cause a false positive result if you have been previously diagnosed with or exposed to other types of coronaviruses. Additionally, if you test too soon, your body may not have produced enough IgG antibodies to be detected by the test yet, which can lead to a false negative result.
This test may NOT be helpful if you:
- Are feeling sick or have had a fever within the last 3 full days, please contact a healthcare provider
- Think you may have an active COVID-19 infection, please contact a healthcare provider
- In the last 10 days, were tested for an active infection, tested positive, and diagnosed with COVID-19, OR had any symptoms of an active COVID-19 infection
- Have a compromised immune system, or have a condition that makes it difficult to fight infections
Sensitivity measures how often a test correctly gives a positive result when a person has the disease. Low sensitivity can result in false negatives, incorrectly identifying sick people as healthy. In the case of COVID-19, a false negative would mean that the test says you do not have antibodies against the virus, when, in fact, you do. The higher the sensitivity, the less chance there will be a false negative result.
Specificity measures how often a test correctly gives a negative result when a person does not have the disease. Low specificity can result in false positives, incorrectly identifying healthy people as sick. In the case of COVID-19, a false positive would mean that the test says you do have antibodies against the virus, when you actually do not. The higher the specificity, the less chance there will be a false positive result.
The specificity of the COVID-19 Antibody test is approximately 100% and the sensitivity of the test is approximately 97.5%.
While these numbers are high, as with many viral tests, there is a chance for a false positive, which means that your result may tell you that you have developed antibodies when you have not.
No, fasting is not required. You may eat as you normally do.
Multiple sources, including the CDC and healthcare experts, recommend you discuss your results and whether to return to work with your healthcare provider.
The COVID-19 Antibody test may also be referred to as COVID-19 Immune Response test or as a SARS-CoV-2 IgG or IgM antibody test. Additionally, you may see the clinical name, SARS-CoV-2 (COVID-19) IgG or IgM SEROLOGY
Individuals can have COVID-19 testing fully paid by their health plan or the government, with no out-of-pocket cost, when billed to the health plan or the government. If you are looking for that no-cost option, contact your healthcare provider.
However, individuals also have the right to have testing that they do not wish to submit to insurance or the government for reimbursement. This option is only for individuals who want to pay directly for the testing and do not want to seek reimbursement from their insurance carrier or the government.