At-home coronavirus swabs could be just as accurate as those performed at clinics

The findings come as the U.S. is facing massive delays in coronavirus testing.

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By Akshay Syal

Swabbing yourself at home for the coronavirus may be nearly as accurate as when the test is administered by health care workers, a research letter published Wednesday in JAMA Network Open suggests.

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.

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When the researchers compared the results, they found that the at-home swab picked up about 80 percent of the positive cases that were found in the clinic, said the study's lead author, Dr. Helen Chu, an infectious disease specialist at the University of Washington. For patients with higher viral loads — meaning they had more virus in their nasal cavities — 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 it identifies positive cases, and the specificity refers to how well it detects negative cases. In both cases, the higher, the better.

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 could help alleviate some of the wait period, Chu said, by not having patients go in for appointments.

"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 of the at-home test used in study is that it was less invasive, with the tip of the swab not being inserted as deeply into the nose as the standard nasopharyngeal swab.

"It's encouraging that similar results were achieved with both," said Tara Smith, an infectious disease epidemiologist at Kent State University. "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."

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 nasal swabs than the average person. But she said that 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 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 that at-home coronavirus tests fared well compared to clinic-administered tests. The study, which was also published in JAMA Network Open, reported that patient-collected swabs were 100 percent as sensitive and 95 percent as specific as swabs collected by health care workers.

Another advantage of testing at home is that "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, referring to personal protective equipment.

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Saskia Popescu, an infectious disease epidemiologist at the University of Arizona, 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 use it correctly, how accurate it is and how long it takes to get results back.

Smith said that with testing labs across the country falling further behind, companies looking to use at-home tests would ideally use separate labs to analyze the results to not overwhelm existing labs.

Referring to an antigen test called polymerase chain reaction, or PCR, Smith wrote in an email: "If these are done by the same companies already doing the bulk of PCR testing, it could possibly worsen the backlog. If it opens up additional avenues for processing (different companies and locations carrying out the analyses), it could help to reduce the backlog."

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