From the Dean: Home COVID tests work

As I mentioned in my column last week, I had the pleasure and honor of welcoming the medical student Class of 2026 to the UND SMHS this past Tuesday. I met with the class in person, although I was masked (as I routinely do when indoors around others). While the latest Centers for Disease Control and Prevention (CDC) community risk assessment remains “Low” for Grand Forks County, many regions of the country and the world are seeing a surge in cases, and to some degree hospitalizations.

In view of this trend, I found a recent scientific study of some importance and relevance. As reported in May in the respected journal Annals of Internal Medicine, the rapid antigen tests that are widely available and easy to use performed quite admirably when compared with the “gold standard” polymerase chain reaction (PCR) test. The rapid antigen tests often are used at home, and they are widely available for personal use (you may pick up free tests on the fourth floor of our Grand Forks building).

The study compared the results of testing with the rapid antigen test with PCR testing. In subjects with presumed high viral loads of SARS-CoV-2, as manifested by lower so-called cycle threshold levels on PCR testing, the home test was positive in about 95 percent of PCR-positive individuals. Reassuringly, it was negative as well in over 99 percent of those without SARS-CoV-2 (that is, those with negative PCR tests). As the presumed viral level (and thus imputed infectivity) decreased, the positivity rate of the home test decreased; in those with the lowest level of presumed viral load, the test was positive only in about 65 percent of PCR-positive individuals. Additionally, the study found that sampling the throat or cheek area was inferior to the usual nasal sampling approach.

There are two important caveats about these results – first, the study was done during the Omicron surge, so we can’t be sure that the results would be the same with the current dominant variants. Second, only the BinaxNOW brand home test produced by Pfizer was studied. I don’t think that either caveat negates the results, but caution in interpreting the data is warranted.

Nevertheless, this study provides further reassurance that we – you, me, our students, faculty, and staff – should have a low threshold for self-testing, especially if we have been in a higher-risk setting, around someone who later developed symptoms, or if we have any reason to be suspicious that we may have COVID-19. I would encourage all of us to self-test as appropriate and recommended. Remember, though, that a single negative home test should not be taken as a guarantee of being disease free, especially if one is symptomatic. Repeat testing, including with PCR, masking, and physical distancing are appropriate in that circumstance.

The bottom line is that using the home tests can help people self-identify those carrying the virus and prompt them to isolate, thus helping to keep the rest of us disease-free. Even if we are done with the pandemic, it is not yet done with us – and these home tests can help us get back to a more normal lifestyle.

Joshua Wynne, MD, MBA, MPH
Vice President for Health Affairs, UND
Dean, UND School of Medicine & Health Sciences