Sean O’Leary, MD, reviews the different types of tests used to detect COVID-19 and their sensitivity and accuracy.
Tina Tan, MD: Can you describe the types of diagnostic tests that are commonly used to detect COVID-19, and how sensitive are these tests at the different stages of infection?
Sean O’Leary, MD: That is a tough question to answer, Dr Tan. I guess what I would say is, on the one hand, what we have within our reach in terms of rapid testing for a relatively newly identified virus, is pretty darn incredible. We have all these at-home tests that people are using, etc. I think much of the American populace has become familiar with the term PCR [polymerase chain reaction test], which they probably hadn’t been before. There are plenty of tests out there. I think they have, in general, been getting better. The problem is that some of these new subvariants may not be as easily picked up. Also, the virus is moving faster than we can possibly move. We can’t anticipate everything, especially every single change in the virus’s genome. Some of these tests may lose some of their sensitivity as these emerge.
I guess the bottom line, I would say is, the PCR tests are still the most accurate. They are going to have the highest sensitivity and specificity. The non–PCR-based tests, like various antigen tests, are pretty specific. If they are positive, it is likely that you have it, but the sensitivity is a little trickier to interpret right now with these new subvariants. The bottom line is that a negative test at one point in time does not necessarily mean you do not have COVID-19. The way I am counseling colleagues and families depends on the setting and on how important this diagnosis is at this moment. If you are going to visit a family member who is undergoing a bone marrow transplant, that is a much different situation than if you live in a household with healthy people, you are not going anywhere, or you are not planning to be out in big crowds. Those are sort of 2 ends of the spectrum. Because with the former case, if you are severely immunocompromised, the risks are still very high. So, you would want to make sure you are not positive for COVID-19.
Transcript edited for clarity