In the study, researchers asked 185 people — most of whom were health care workers — who were tested for the coronavirus in a clinic to test themselves again the next day, at home, using a nasal swab.
When the researchers compared the results of the two tests, they found that the at-home swab picked up about 80 percent of the positive cases that were found in the clinic, lead study author Dr. Helen Chu, an infectious disease specialist at the University of Washington, said. For patients with a higher viral load — meaning they had more virus in their nasal cavity — the at-home test picked up 95 percent of the positive cases that were found in the clinic, Chu said.
In particular, the at-home swabs were 80 percent as sensitive and 97 percent as specific as the tests administered in the clinic, the study found. A test’s sensitivity refers to how well the test identifies positive cases, and the specificity refers to how well it detects negative cases. In both cases, the higher, the better.
The findings come as the U.S. is facing massive delays in coronavirus testing, with reports of some people having to wait up to two weeks to get results back.
An at-home swab can help alleviate some of that wait period, Chu said, by not having patients come in for an appointment.
“There’s no delay that’s introduced by having to first call the clinic and then make an appointment and then come in and then have the swab collected. You have a test kit sent to your house,” she said. Getting results back, however, could still be delayed by bottlenecks at labs.
Another advantage to the at-home test used in study is that it was less invasive, with the tip of the swab not being inserted as deep into the nose as the standard nasopharyngeal swab.
“It’s encouraging that similar results were achieved with both,” Tara Smith, an infectious disease epidemiologist at Kent State University, said. “Nasopharyngeal swabs are tough even for health professionals to take correctly, so if we can get similar results from a swab that’s less invasive, that’s a positive outcome in my book.”
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Smith, who wasn’t involved with the research, noted that the majority of the people in the study were health care workers, meaning they might have more familiarity with administering a nasal swab than the average person. But, she said, in her own research, her team has used self-collected nose and throat swabs for other pathogens in populations of rural Iowans with success, adding that she’s “hopeful that similar results will be found in general populations with COVID testing.”
Chu, the study’s lead author, also has past experience with at-home testing studies. She had been studying the effectiveness of at-home swabbing for influenza in a project called the Seattle Flu Study.
An earlier study, from researchers at Stanford University, also found at-home coronavirus tests fared well compared to clinic-administered tests. That study, also published in JAMA Network Open, reported thatpatient collected swabs were 100 percent as sensitive and 95 percent as specific as the swabs collected by health care workers.
Another advantage for “testing at home means they don’t have to expose others at clinics, and can save on PPE necessary for health care workers who would otherwise be taking patient swabs,” Smith said.
Saskia Popescu, an infectious disease epidemiologist at the University of Arizona, also said that at-home testing can be beneficial, but noted that there are some concerns, including how easy the test is to use, whether people are using it correctly, the test’s accuracy and the turnaround time to get results.
With testing labs across the country facing mounting backlogs, Smith said companies looking to use at-home testing would ideally use separate labs to analyze the results, to not overwhelm existing labs across the country.
“If these are done by the same companies already doing the bulk of PCR testing, it could possibly worsen the backlog,” Smith wrote in an email. “If it opens up additional avenues for processing (different companies and locations carrying out the analyses), it could help to reduce the backlog.”