Max Hamilton found out that his roommate had been exposed to the coronavirus shortly after Thanksgiving. The dread set in, and then so did her symptoms. Wanting to be cautious, she continually tested, remaining masked in all common areas of the house. But after three negative rapid tests in a row, she and Hamilton felt the worst was over. At the very least, they could safely chat at the kitchen table, right?
Wrong. More than a week later, another test finally produced a second line: bright, pink, positive. Five days after that, Hamilton also tested positive. This was his second bout of COVID since the start of the pandemic, and he wasn’t feeling as well. Congestion and fatigue aside, he was “very frustrated,” he told me. He felt that they had done everything right. “If we have no idea if someone has COVID, how are we supposed to prevent it?” He now has a different opinion about rapid tests: they are not guarantees. When he and his roommate return from their Christmas and New Year vacation, he said, they will stay away from friends showing any symptoms.
Hamilton and his roommate are just two of many who have been aggrieved by the rapid. Since Omicron’s inception, for one reason or another, false negatives seem to be popping up. with more frenquency. That leaves people stuck trying to figure out when, and if, to trust the simplest and easiest way to check for COVID status. At this point, even people who work in healthcare are freaking out. Alex Meshkin, CEO of the Flow Health medical laboratory, told me that he spent the first two years of the pandemic carefully masking in social situations and asking others to get tested before meeting with him. He then got sick with COVID shortly after visiting a friend who didn’t think she was sick. It turns out that he had only done a quick test. “That is my wonderful personal experience,” Meshkin told me. Your takeout? “I don’t trust the antigen test at all.”
That could be a bit extreme. Rapid antigen tests still work, and we know the problem of late positivity for centuries. In fact, the tests are as good at detecting the SARS-CoV-2 virus now as ever, Susan Butler-Wu, a clinical microbiologist at the University of Southern California Keck School of Medicine, told me. Her detection limit, the lowest amount of viral antigen that will reliably register as a positive result, didn’t really change as new variants emerged. At the same time, the Omicron variant and its derivatives appear to take longer, after infection onset, to accumulate that much virus in the nose, says Wilbur Lam, a professor of pediatrics and biomedical engineering at Emory University who is also a one of the principal investigators evaluating COVID diagnostic tests for the federal government. Lam told me that this delay, between getting sick and reaching the minimum detectable concentration of the viral antigen, could be contributing to the spate of false-negative results.
That issue is not likely to be resolved anytime soon. The same basic technology behind rapid COVID tests, called “lateral flow,” has been around for years; it’s even used for standard pregnancy tests, Emily Landon, an infectious disease physician at the University of Chicago, told me. Oliver Keppler, a virology researcher at the Ludwig Maximilian University of Munich, who participated in a to study Comparing the performance of rapid tests across variants, he says there isn’t really a way to modify tests to be more sensitive to newer variants. “Conceptually, there’s little we can do.” In the meantime, he told me, we have to accept that “in the first day or two of infection with Omicron, on average, the antigen tests are very bad.”
Of course, Hamilton (and his roommate) would point out that the tests can fail even several days after symptoms begin. That is why he and others are hesitant to trust them again. “It’s not just about the usefulness or accuracy of the test. It’s also about the willingness to even get tested,” Ng Qin Xiang, a preventive medicine resident at Singapore General Hospital who participated in a to study examining the performance of rapid antigen tests, he told me. “Even within my circle of friends, many people, when they have respiratory symptoms, just stay home and rest,” she said. They just don’t see the point of testing.
Landon recently contracted COVID for the first time since the start of the pandemic. When his daughter came home with the virus, he decided to conduct his own experiment. He kept track of his rapids, testing every 12 hours and even taking pictures as proof. His symptoms began on a Friday night and his initial test was negative. So it was on Saturday morning. However, by Saturday night, a faint line had begun to appear, and by the next morning, 36 hours after symptom onset, the second line was dark. Her advice to those who want the most accurate result and don’t have as many tests to spare is to wait until you’ve had symptoms for two days before testing. What if he’s been exposed, he has symptoms, and he only has a test? “You don’t even need to bother. You probably have COVID.”