Understanding Sensitivity and Specificity
People keep talking about test sensitivity and specificity of an antibody test, such as the COVID-19 Antibody test. What does this mean?
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, or the virus itself, 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, or the virus itself, when you actually do not. The higher the specificity, the less chance there will be a false positive result.
What is the sensitivity and specificity of the COVID-19 Antibody test?
Quest Diagnostics only uses a SARS-CoV-2 Antibody (IgG), Spike, Semi-quantitative test from manufacturers who demonstrated robust validation of their test kits. Highlights of this validation include:
• Sensitivity is greater than 99.9%. This is dependent on the timing of the sample collection from when a patient is exposed to the SARS-CoV-2 virus or starts having symptoms.
• Specificity is approximately 99.9%.
Note: Positive results may also occur after a COVID-19 vaccination, but the clinical significance is not known, nor is it known how good this test is at detecting antibodies in those that have been vaccinated. Additionally, how long antibodies remain detectable after infection or vaccination and how long protection, if any, may last is also not known. The results of this test should not be interpreted as an indication of degree of immunity or protection.
What does the sensitivity and specificity of the COVID-19 Antibody test mean for me?
The specificity of the COVID-19 Antibody test (SARS-CoV-2 Antibody [IgG], Spike, Semi-quantitative) is approximately 99.9% and the sensitivity of the test is greater than 99.9%.
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.