False negative results can sometimes occur. This can happen if you get an antibody test too soon after being exposed or vaccinated and your body has not yet made enough antibodies to be detected by the test. It can also happen in individuals with weakened immune systems who may not develop detectable levels of antibodies after exposure or vaccination.
False positive results can sometimes occur. This can happen if the test detects antibodies from other coronaviruses you may have been exposed to, like the viruses that cause the common cold.
A negative antibody test does not rule out previous infection. A proportion of persons who are infected with SARS-CoV-2 might not develop measurable antibodies.
If you are concerned about your results, it is important to follow up with a healthcare provider, who can evaluate your medical history.