Frequently asked questions about Antibody Tests

Does this test check to see if I am immune to COVID-19?


Yes. However, to what extent is still unknown. Your immunity may be a lesser resonse to the virus in the future or complete immunity. It is also unknown exactly how long immunity will last.




When should I have this test done?


Natural infection: At least 7 days after end of symptoms since most people recover in 14 days after onset of symptoms OR 20+ days after first syptoms are noticed. Research has shown that nearly everyone with COVID-19 (Coronavirus disease 2019) developed antibodies by day 20 after symptoms. If you test too early, it is possible that the IgG antibody response (seroconversion) may not have occurred yet. After Vaccination: 14 days after vaccination to check that you have made antibodies against the virus. Depending on vaccine, a second injection may be needed to increase antibody response. If a second vaccine is needed, a repeat antibody check can be done 14 days after that injection. Before Vaccination: If you have had or suspect a previous infection of COVID-19, checking antibodies could help you determine the need for the COVID-19 vaccination.




Does a postive antibody test mean I'm a carrier or contagious in any way?


You could be contagious if you test for antibodies early enough to still have an active infection. You should wait until at least 7 days from the end of symptoms.




What is a false negative/false positive antibody result? How likely are they?


A false negative result is when a patient is/was infected by SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) but their antibody result is negative, while a false positive result is when a patient has not been infected by SARS-CoV-2 but tests positive for antibodies. False positives are likely caused by past viral infections, while false negatives are due to when the test was taken or if an individual has a weak antibody response. There are no reference specimens to work with currently, so the only way to determine a false positive is to test samples collected in 2019 and earlier (prior to first COVID-19 cases) and to cross compare testing. The gold standard now is to compare antibody results with PCR testing, which is flawed because of the possibility of PCR false negatives (false positives with PCR testing only come from reagent or sample contamination). Sensitivity and specificity testing of our IRB-approved study samples indicate a very low number of potential false positives and false negatives. Running two separate antibody tests as we do for ZRT’s COVID-19 Dual Antibody Test helps confirm true positive/negative antibody results.




If I am positive for antibodies, does that mean I will always be protected from COVID-19?


Currently is it not clear whether detection of IgG antibodies infers immunity to future COVID-19 (Coronavirus disease 2019) infections. Studies have indicated neutralizing ability of IgG antibodies against SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) in animals, but results need to be looked at with caution. Duration of any immunity is still unknown.