Antibodies are proteins that attack foreign invaders in the body. The presence of antibodies for SARS-COV 2 (the virus that causes the disease COVID-19) in your blood would indicate that your immune system has battled the new coronavirus. Antibody tests are typically conducted via a blood draw after a person has recovered, whereas a nasal swab is used to diagnose an active coronavirus infection.
The accuracy of an antibody test depends on two factors: sensitivity and specificity. Sensitivity gauges whether the test can pick up on the antibody if it’s present, and the specificity gauges whether the test can distinguish SARS-COV 2 antibodies from antibodies to the six other known coronaviruses, including some of the viruses that cause the common cold.
A test that is 95% specific will give false positives 5% of the time. That is, in 5% of cases it reports the presence of antibodies when there really are none. False positives are more likely in places where the new coronavirus has not been prevalent. In a population of 1,000 people, if 1% of the people have been exposed to the coronavirus, an antibody test with 95% accuracy will give 50 false positives and just 10 true positives. So only 1 in 6, or 16.6%, of people testing positive would actually have antibodies, according to a calculation for MONEY by Marm Kilpatrick, a professor who studies infectious diseases at the University of California, Santa Cruz .
But the results look different in a place like New York City, the pandemic’s epicenter, where preliminary data last month found that around 21% of residents had tested positive for antibodies. With that level of the population exposed, in a test with 95% accuracy, there would be 210 people who are true positives and 50 false positives, so 80.7% of those testing positive would actually have antibodies.
With all of that being said...we are offering the Roche test through LabCorp with a 100% Sensitivity and a 99.8% Specificity for $100.