Antigen tests may be less sensitive at detecting the Omicron variant of SARS-CoV-2, particularly early in infections, the New York Times reports.
The Times reports that many test makers have said their tests can detect Omicron, especially at high levels, but that some emerging, small studies have suggested that they may be less sensitive at doing so. It adds that the US Food and Drug Administration recently noted the possibility of decreased test sensitivity.
For instance, a new preprint posted to MedRxiv studied 30 individuals who underwent both rapid antigen and PCR testing through a workplace initiative to find that a positive antigen test lagged about three days behind that of a positive PCR test. Another recent preprint additionally found differences in the ability of nasal swabs versus saliva samples to detect Omicron.
"The message is not that we should stop using these tests," Isabella Eckerle from the University of Geneva tells the Times. Rather, test results should be interpreted with care and with the recognition that results are "not a ticket that allows you to go back to normal or to drop any other measures," she adds.