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Coronavirus FAQ: Why are some folks hacking home COVID tests by swabbing their throat?

A COVID-19 home test in the U.S. comes with a swab to swirl in the nostrils. But some users say they're swabbing the throat, too — even though that's not what the instructions say. "They may stab themselves," cautions Dr. Janet Woodcock, acting head of the FDA.
Angus Mordant/Bloomberg via Getty Images
A COVID-19 home test in the U.S. comes with a swab to swirl in the nostrils. But some users say they're swabbing the throat, too — even though that's not what the instructions say. "They may stab themselves," cautions Dr. Janet Woodcock, acting head of the FDA.

Lots of folks on Twitter say that swabbing your throat in addition to your nose may be a better way of using your COVID-19 testing kit to detect the omicron variant. Is this true?

If you've used a do-it-yourself COVID-19 home test in the U.S. — the "antigen" rapid tests that promise results in 15 minutes or so — you know the drill. You typically swirl a cotton swab around in your nostrils, mix it with some liquid and then drop it on a test strip to await the results: positive or negative for the coronavirus.

But in recent weeks, there has been an online debate about where to stick that cotton swab. Although the directions specify a nasal swab on U.S. products, some medical professionals believe the test is more effective at detecting the coronavirus, and specifically the omicron variant, if the kit's swab is used in the throat and/or cheek in addition to the nose.

Why did this hack emerge — and is there any medical science to back it up?

The idea of a throat swab is not in and of itself a radical step. Even though antigen test kits in the U.S. are designed for a nasal swab, home tests are designed for a throat swab in other countries — in Canada and the U.K., for example.

The idea of improvising with a throat swab is connected to the omicron variant, which was identified in late November and has swept the world. Researchers increasingly believe omicron may replicate in the throat before the nose.

That was one of the findings of a study conducted at the University of Cape Town in South Africa. Researchers examined the ability of PCR tests to detect the variant by comparing diagnostic tests for 382 symptomatic COVID-19 patients who weren't hospitalized. In patients with the delta variant of the coronavirus, saliva swabs detected the virus 71% of the time, while nasal swabs found it 100% of the time. But in patients with omicron, researchers found the reverse: Saliva swabs detected the virus 100% of the time, while nasal swabs caught it 86% of the time.

The research has not been peer reviewed. And the tests used in the study were PCR tests, not antigen tests. (PCR tests are the gold standard and are administered typically in a health care facility; antigen tests are less precise and can be done at home. See this story for details on the differences.)

Nonetheless, the South African study has led some epidemiologists and immunologists in the U.S. to experiment with antigen tests by swabbing their throats or cheeks in addition to the nose when administering a self-test.

That's not an authorized use of the kits, reminds the Food and Drug Administration, which regulates the kits: "FACT: When it comes to at-home rapid antigen #COVID19 tests, those swabs are for your nose and not your throat," it said in a tweet issued on Jan. 7.

And even proponents of the throat swab stop short of endorsing the practice for the public without a green light from the FDA.

One of the most often quoted voices in favor of throat swabbing is Dr. Michael Mina, formerly an epidemiologist and immunologist at the Harvard T.H. Chan School of Public Health and now the chief science officer at the testing company eMed. He has tweeted: "We should be rigorously looking into throat swabs to add some level of sensitivity" and "Throat swab + nasal may improve chances a swab picks up virus."

But Mina has gone on to tweet that the FDA was right to warn the public not to go against manufacturer's directions: "Telling US public not to go against directions is the *right* thing to do."

"The tests haven't been designed to do [throat swabs], so we don't know whether there are false positives or negatives," agrees Dr. Jill Weatherhead, assistant professor of adult and pediatric infectious diseases at Baylor College of Medicine. "It logically makes sense that you'd want to do it, but that's not how [the tests have] been developed or tested."

One potential problem could be the thicker viscosity of throat saliva, says Dr. Yuka Manabe, associate director of global health research and innovation and a professor of medicine at the Johns Hopkins Bloomberg School of Public Health. It's possible the sample would need to be filtered first, she says, to produce an accurate result.

That's not necessarily a critical concern, says Michael Daignault, an emergency physician who serves as chief medical adviser to Reliant Health Services, a medical testing company. He says that the nature of throat saliva could simply cause the test to display a message that the result is invalid rather than a false positive.

Another obvious potential problem, Manabe points out, is the length of the swab in some of the kits: "The swab that you use doesn't have a very long stick because it's just meant to be used in the front of your nose. So for you to get that into the back of your throat would not be very easy, truthfully, for some of the kits, depending on the length of the swab."

The public debate about the best way to swab has prompted a growing chorus of voices to call for new studies and a revamping of the kits and/or the instructions.

That kind of change is what Michal Tal is hoping for. Tal, an instructor at Stanford University's Institute for Stem Cell Biology and Regenerative Medicine and a visiting scientist at the Massachusetts Institute of Technology, is a proponent of throat swabs. Before seeing anyone in person, she asks that they take a coronavirus test and swab not only their nose but their cheeks, the roof of their mouth, under their tongue and — if they don't gag easily — their throat near the tonsils.

"I'm feeling very frustrated that the FDA and CDC didn't jump on this and try to make more rapid changes," says Tal. "The virus is always two steps ahead and we don't adapt."

At a congressional hearing Monday, the acting head of the FDA, Dr. Janet Woodcock, noted that the National Institutes of Health has helped accelerate the authorization of new home tests so that they can get the FDA's signoff in just one or two days. But she said it may take a while for companies to change their test configurations to include larger swabs for the throat.

In the meantime, she warned people not to swab their throats with the current devices, which are designed as nasal swabs. "They may stab themselves," she said. "That would not be good."

Sheila Mulrooney Eldred is a freelance health journalist in Minneapolis. She has written about COVID-19 for many publications, including The New York Times, Kaiser Health News, Medscape and The Washington Post. More at sheilaeldred.pressfolios.com. On Twitter: @milepostmedia.

Copyright 2022 NPR. To see more, visit https://www.npr.org.