Nursing home operators may have better luck using saliva-based, rapid antigen testing for screening COVID-19 within their facilities over polymerase chaise reaction (PRC) nasal swab because of the tool’s ability to judge how infectious people are, a pair of researchers suggested in a new blog published in Health Affairs.
Investigators A. David Paltiel, MBA, Ph.D., and Rochelle Walensky, M.D., explained that while testing to diagnose COVID-19 helps identify a person with the disease, surveillance testing helps determine how infectious a person is who may have been exposed to the disease.
They added that though rapid saliva-based antigen test has shown a 30% false negative rate and does a poor job of diagnosing infection, it’s “likely the better tool for judging infectiousness.” That’s beneficial to people who live and work in close proximity to others, like in a nursing home.
“For purposes of surveillance screening, those antigen-based negatives worrying the FDA aren’t false negatives at all; those are true negatives for disease transmission. Far from being problematic, in the context of outbreak containment, the antigen test’s limited window of sensitivity is a major asset,” Paltiel and Walensky wrote. Paltiel serves as a professor at the Yale School of Public Health, while Walenskey is the chief of infectious diseases at Massachusetts General Hospital (MGH) and medicine professor at the Harvard Medical School.
“The antigen test is ideally suited to yield positive results precisely when the infected individual is maximally infectious,” they added.
In contrast, PCR testing is “far too prone to false positives” when used as a test of infectiousness.
“For purposes of containing outbreaks, the problem is decidedly not false negatives associated with antigen testing; rather, the problem is false positives associated with PCR testing. If your goal is to suss out infectiousness and prevent outbreaks, the antigen test is the tool you want to reach for first,” the researchers wrote.
The federal government has shipped point-of-care antigen testing tools to every nursing home in the United States as an effort to combat the disease.
