Researchers are working to figure out whether and why rapid tests may be less able to spot Omicron SARS-CoV-2 infections and use that information to improve the tests, NPR reports.
It notes that Emory University's Wilbur Lam and his team are among those assessing rapid tests — his lab, NPR adds, found that some rapid antigen tests did not detect the Omicron variant when it was present at a concentration at which other variants would have been caught, a finding that led to the Food and Drug Administration to warn in December that such tests might have reduced sensitivity. Lam and his colleagues have since been found, like some other small studies, that rapid antigen tests seem to best detect the Omicron variant when people are symptomatic and have high viral loads.
NPR notes that the problem with tests could stem from people developing symptoms earlier with Omicron than with other variants, so the tests don't then pick up the infection for another day or two. There further are some indications that the variant may instead lead to higher viral loads in the throat or mouth, rather than in the nose where samples for testing are obtained.
These and other findings could help test makers update their tests by, for instance, including a throat swab, NPR says.