Rapid tests are being used at home and in schools to help catch COVID-19 cases early and help keep the virus from spreading. But the tests may offer a false sense of security, as the FDA has acknowledged that some may be less sensitive in detecting the omicron variant.
Rapid tests have been in short supply, but now, as production ramps up and the government begins shipping tests to people’s homes, there are new questions about how reliable they are, especially among people who don’t have symptoms. The NIH is now involved to test the tests to see how they stack up against the omicron variant.
How Accurate are At-Home COVID Tests?
At-home rapid tests can be used to quickly screen for COVID – delivering results in as little as 15 minutes – but they’re not always accurate.
"There's quite a bit of variability from test to test, and even within one test, there's some variability in performance between the different variants of concern that have popped up," said Dr. Wilbur Lam, a physician at Emory University.
Dr. Lam's lab has been working closely with the NIH and the FDA to test the performance of different antigen tests on the market.
He says early results suggest some tests aren’t as effective at detecting the highly contagious omicron variant.
Full coverage of the COVID-19 outbreak and how it impacts you and our communities
"No test is perfect. And even before omicron, when these rapid tests came about, we've always known that people with symptoms, they produce more virus. So therefore it's easier to catch," Dr. Lam said.
When Should You Take an At-Home COVID Test?
Studies show that rapid tests work best when they’re taken two to five days after an exposure in people who are experiencing symptoms. But they may not be as reliable among those who are asymptomatic, which is why health experts say it’s best to test yourself more than once.
"Getting a negative test is not a free pass to do whatever. I think everyone has to be aware that one can get a false negative, especially if there's no symptoms," Dr. Lam said.
"If I'm going to visit a family member who's elderly and or has a chronic illness that might be at risk, I might test myself more than once," he said.
Does Your Vaccination Status Affect an At-Home COVID Test's Accuracy? Is Throat Swabbing More Accurate?
Dr. Lam’s team is also studying whether someone’s vaccination status may impact the results of a rapid test. They're also experimenting with different testing methods to see if adding a throat swab, in addition to nasal swabbing, could lead to more accurate results.
"So what we're doing right now at our center is really asking this question of, where does omicron live and when? And to really build up any evidence at all for changing the guidelines," Dr. Lam said.
For now, the FDA is urging people to avoid doing a throat swab because that’s not how these rapid tests were designed.
How Well Do At-Home COVID Tests Work for Omicron?
The science is improving, and Dr. Lam says two new tests will soon be available, using technology that’s better at detecting omicron.
"Two tests that are coming onto the market this week or maybe [in the] next two weeks that are made by Roche and Siemens. And those tests came through our new kind of omicron testing process," Lam said. "And those work and the FDA looked at our data and immediately authorized."
He says those particular tests were specifically tested using live omicron samples with sensitivity rates between 80% and 90%.
While some rapid tests may potentially miss an infection, Dr. Lam says they’re still a powerful weapon to have during the pandemic.
"When they're available, they're easy to use, they're very convenient and you can get multiple uses over time," Dr. Lam said.
Availably has been a big issue, too. The new tests by Roche and Siemens are now available online and will soon be in stores.
When it comes to testing, the PCR is still the gold standard and the most accurate, but it has to be processed in a lab and it can take several days to get your results.
According to the CDC, most antigen tests have a sensitivity rate that ranges from 50% to 70%.