COVID at-home tests are meant for nasal passages, not throat: experts

January 8, 2022
COVID at-home tests are meant for nasal passages, not throat: experts
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It’s never been harder for Americans to get their hands on at-home rapid tests, as the fast-moving omicron variant fuels more than half a million new COVID-19 cases each day. 

The lucky ones with tests don’t want to waste them. 

Early data suggests virus particles from COVID variants – including omicron – may appear in the throat before reaching nasal passages where test swabs are done. And federal regulators warn the rapid tests in general may not be as effective detecting the new variant. To make sure they don’t miss an infection, some have opted to add a swab to the back of their throat as well as their nose. 

But federal agencies and health experts urge that at-home tests be used as directed and to not add a throat swab – for now. Throat swabbing may be called for in the future, experts say, but the tests currently authorized in the U.S. weren’t manufactured to detect virus in a person’s throat and could deliver false results.

“The thing about anything you do at home is that people are free to use these tests however they want to use them. That’s the democracy of at-home testing, right?” said Dr. Emily Volk, president of the College of American Pathologists. “But they need to do the test as prescribed. They’re not FDA-authorized any other way.”  

The idea of throat swabbing gained popularity after the Food and Drug Administration announced last week rapid antigen tests may lose some of their sensitivity to the omicron variant.

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The FDA warning was followed by a preprint study published Wednesday that gained traction on social media and casted more doubt on rapid antigen testing.

The study, which hasn’t been peer-reviewed, tracked 30 people in New York and California who were tested daily with a polymerase chain reaction, or PCR, test using saliva and a rapid antigen test using nasal swabs. Researchers found all the antigen tests produced false-negative results, and in 28 of the 30 people their viral loads were high enough to infect other people.

Dr. Michael Mina, an infectious disease expert and former Harvard professor who now serves as chief science officer of the testing company eMed, said the study’s findings don’t show rapid antigen tests can’t detect omicron. 

What they show is that tests are able to detect virus particles in the saliva earlier than in the nasal cavity. 

“Does that mean we have to throw away nasal swabs as a solution? Absolutely not,” said Mina, an outspoken advocate for frequent rapid testing to control virus spread. However, the mutating virus “looks like it’s starting to transmit at lower viral loads before the virus grows up enough to start getting into the nose.”

The biggest risk people take by swabbing their throat is not doing it right, said Dr. Michael Blaivas, chief medical officer of Anvasi Diagnostics, a diagnostic technology company.

Virus particles are most concentrated in the oropharynx located at the back of a person’s throat, which can be difficult to reach with an ordinary nasal swab. Missing the area could produce a false negative result because not enough virus was collected.

“Putting a swab inside your nose and running it around is pretty easy for anybody to do, whereas swabbing the back of your throat sounds easy but it’s really hard,” he said.

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Abbott Laboratories, which makes BinaxNow antigen tests, said it has reviewed “every published study” and completed “extensive testing” on samples from omicron patients.

“In all cases, our studies confirm that BinaxNow continues to detect the omicron variant at comparable viral load levels as all other variants and the original SARS-CoV-2 strain,” said John Koval, director of public affairs at Abbott. He emphasized the company’s test is “indicated for nasal use only.”

With at-home tests hard to come by hard to come by, Volk said throat swabbing is too much of a gamble and Americans shouldn’t waste tests by risking undependable results.

“These collection devices are designed very specifically to do the job that they do,” she said. “Using them for another purpose is not a good idea.” 

Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT. 

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

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