An article recently published in The Baltimore Sun reviewed various COVID-19 tests, with Bobbi Pritt, M.D., and Matthew Binnicker, Ph.D., among the experts offering insight on testing accuracy, as well as circumstances that could affect a test's reliability.
Dr. Pritt, chair of the Division of Clinical Microbiology, says with the improvement of PRC tests, retrieving samples from deep within the nasal cavity using a long swab is no longer always necessary to obtain accurate results.
"We can accept nasal swab specimens and even saliva, and perform testing on those specimens, and if they are collected correctly the results can be just as good as those that are collected using that gold standard nasopharyngeal swab," Dr. Pritt says.
Dr. Binnicker, director of Mayo's Clinical Virology Laboratory, notes that test timing, as well as the quality and type of sample, can have an impact on COVID-19 test accuracy. He adds that repeat testing may be necessary if a negative COVID-19 test is followed by negative results for similar conditions, and symptoms continue.
"If a COVID-19 test is negative, then specific testing for influenza will also need to be performed," he says. "If the results are negative for these viruses and the patient continues to be ill, a repeat COVID-19 test can be appropriate. As patients enter into the second week of illness, a lower respiratory sample (e.g., like sputum) is preferred over an upper respiratory swab to increase the likelihood of detecting SARS-CoV-2 during the later stages of disease."
Dr. Pritt also addresses the accuracy and appropriate use of antigen tests, saying: "If we are screening large numbers of individuals, and we plan on doing that on a regular basis, let's say college students on a weekly basis, then using an antigen test is probably going to be the best strategy forward because it's going to be relatively inexpensive and easy to do, and it's going to be done on a relatively lower risk population."