The mouth method might be better at detecting omicron by Shannon Palus (Slate)

 

 

Earlier this month, Jacklyn Grace Lacey tested herself for COVID-19 using a home kit. First, she did it the usual way, sticking the swab up her nose. It came back negative. Instead of stopping there, Lacey, who works as a medical anthropologist at the American Museum of Natural History, “decided to bio-hack on myself.”

The omicron variant was circulating quickly around New York City, and the literature suggested that the variant might replicate faster in the piping of one’s lungs, as opposed to one’s nasal cavity. So she did another test, sticking the swab down her throat. This time, the test yielded that telltale pink line.

Lacey, who had stocked up on rapid tests over the summer, took this as a clear sign she had COVID—but she kept swabbing via the traditional method out of curiosity. After 36 hours, Lacey finally got a positive result from a nasal swab, too. “I was pleased to learn my hypothesis was correct,” she told me via Twitter DM (she was still sick and not up for talking on the phone). But she was concerned about what her experiment might mean for others who were relying on tests to screen before holiday gatherings. She changed her name on Twitter to “Throat Swabs 4 Omicron ASAP.” Before long, she was retweeting someone else who got a positive with the same method.

Throat swabs, really? Yes, really.

If you’re so inclined, you can swab your throat with a standard test kit by opening wide in front of a mirror and sticking the thing to the very back of your mouth, behind the arch. (A strep test, basically.) Then, stick the swab in each of your nostrils, as the instructions on the rapid test explain. While adding the throat sample is not approved by the Food and Drug Administration for kits in the U.S., it’s standard in other places, like the United Kingdom.

Given how omicron has mutated, it’s possible it should be standard here. Michael Mina, the epidemiologist who has been clamoring for more rapid tests since the early days of the pandemic, is another loud proponent of the throat swab. “Throat swab + nasal may improve chances a swab picks up virus,” he tweeted Monday.

The case for sweeping a swab around the back of your mouth in the age of omicron has some evidence to back it, if you’re willing to go by a couple of preprint papers. One published on the University of Hong Kong’s website by public health and pathology researchers on Dec. 15 explains that omicron “multiplies 70 times faster than the Delta variant and original SARS-CoV-2 in human bronchus.”

Another published on medRxiv on Dec. 24 describes test results from 382 patients at a hospital in Cape Town, South Africa. Patients tested themselves with both nasal and saliva swabs (which is different than a throat swab). The nasal swab method successfully caught all of the delta cases—but it missed 15 percent of those caused by omicron. In contrast, the saliva swab caught all of the omicron cases. (Mileage may vary with home tests; these were PCRs. Also keep in mind that people were recruited because they were already known to have COVID.)

These findings, combined with the reports of people coming down with streplike symptoms, convinced Michal Caspi Tal, an immunologist at Stanford, to shift her own home-testing methodology: She uses one swab for both her mouth and her nose. “It’s so gross,” she says. But she feels that it’s important for getting the most accurate result possible: “I just want to be sure it’s negative.”

Throat swabbing is “all upside except for the hassle,” agrees Chana Davis, the founder of Fueled by Science who covers rapid testing for Dear Pandemic. She started swabbing her throat (as well as her nose) after her son recently tested positive for the virus using the traditional method with a rapid test.

The fact that throat samples are standard in some other countries made her comfortable going “off protocol” with a rapid test, which are only authorized for nose-swabbing by the Food and Drug Administration. Not everyone in her household is on board with doing a throat swab on themselves, she says: “My husband hears me gagging in the bathroom and thinks it’s not worth it.”

It’s actually pretty easy to do (though this reporter can confirm it may trigger the gag reflex). A video from the U.K. Health and Security Agency explains how: Or you can do a cheek swab method, which is what Tal uses. She follows the instructions described in the Cape Town study, in which participants were asked to swab on the inside of both cheeks, above and below the tongue, on the gums and hard palate. A minimum swabbing duration of 30 seconds was required.

No matter which method you use, do not eat, drink, or use toothpaste for half an hour before, as it could potentially cause a false positive. Which method—throat swabbing or saliva—is better, and how necessary is adding this step really? Hard to say. Almost everyone I spoke to emphasized the need for more data, especially when it comes to rapid tests in the U.S., which are not approved by the FDA for throat swabbing.

“What I’m looking for would be a time series study—looking at testing people who have been exposed and then have them regularly test (rapid or PCR), using nose and throat swabs,” Tara Smith, an epidemiologist at Kent State University, told me via email. One of her questions is whether the pH of the buffer—that’s the liquid in your home kit—is suitable for testing swabs that have been stuck down your throat. “With the administration offering rapid tests soon, I think we need good data that is omicron-specific to really know how good they are with detecting it at all,” Smith added.

The FDA shared Tuesday that preliminary data suggests some antigen tests may be less sensitive to omicron, though Mina has pushed back on this report, calling it a “remarkably vague” swipe at a critical tool. As my colleague Aaron Mak reported last week, there is good reason to think that rapid tests in general will work somewhat reliably with omicron, based on where the variant is mutated—but there can be a gap between when symptoms occur for vaccinated people and when there’s a high enough viral load for a test to turn up positive on a rapid. (As always, a PCR will be more sensitive, and might be the right choice if you’re vaccinated, symptomatic, and can swing an appointment.)

This all highlights two important lessons that I’m sure you’ve heard a thousand times: A negative on a rapid test isn’t you’re-definitely-free-of-the-virus permission slip. And, as Tal put it, “we’re always two steps behind the virus.” The fact that we’re all kind of hunting and pecking for guidance is especially worrying. “It’s scary and disconcerting that people are getting their information from Twitter because the government can’t get us the information we need,” says Davis. But Twitter has in this instance offered up reasonable advice, via Lacey: If you’re fortunate enough to have rapid antigen tests on hand, go ahead and try swabbing your throat.

 

“Good Grief, We’re Doing Throat Swabs Now?” Slate