The suggestion to add a throat swab has been gaining attention on social media recently, at the same time that concerns have been rising about the efficacy of at-home tests. The FDA announced in late December that while rapid antigen tests do detect the omicron variant, some “may have reduced sensitivity,” citing an early finding from ongoing performance evaluations. A more recent small study, which hasn’t been been peer reviewed, reported that people in workplaces who had omicron tested positive on saliva-based PCR tests several days before their infection was detected by rapid antigen tests using nasal swabs.
Some prominent experts have also started recommending the additional throat swab.
Because symptoms appear to be starting earlier in people infected with omicron, “there is a chance the virus isn’t yet growing in the nose when you first test,” tweeted epidemiologist and testing expert Michael Mina, a vocal advocate of rapid testing who recently left his academic and research positions at Harvard and is now chief science officer for the biotech software company eMed.
“Virus may start further down,” Mina continued. “Throat swab + nasal may improve chances a swab picks up virus.”
The recommendation to swab your throat and nose is driven by a “confluence of data,” Feigl-Ding told The Washington Post in an interview.
In addition to the anecdotal reports, Feigl-Ding pointed to some early research in support of the extra swab. Research uploaded to the University of Hong Kong’s website on Dec. 15 found that omicron “infects and multiplies 70 times faster than the Delta variant and original SARS-CoV-2″ in the human bronchial tubes, which carry air from your windpipe into your lungs. Meanwhile, researchers in South Africa shared findings suggesting that saliva swabs may be better than nasal swabs at detecting omicron, because there may be higher levels of the virus in saliva. He also noted that the recent workplace study involving rapid antigen tests bolsters the evidence that saliva samples could be better.
Those research papers were released as preprint articles, meaning formal peer review of the work has not been completed.
“This is a precautionary approach,” he said of adding a throat swab to a standard nasal swab. “It’s based on evidence and data, based on experts, based on not just single anecdotes, but many anecdotes, and based on other countries.”
But the FDA, which issues emergency use authorizations for coronavirus tests, has strongly discouraged deviating from the specific instructions that accompany test kits.
“The FDA advises that COVID-19 tests should be used as authorized, including following their instructions for use regarding obtaining the sample for testing,” the federal agency said in an emailed statement to The Post on Wednesday.
The agency added that it has “noted safety concerns regarding self-collection of throat swabs, as they are more complicated than nasal swabs — and if used incorrectly, can cause harm to the patient.” (The Centers for Disease Control and Prevention recommends that throat swabs should be collected by a trained health-care provider.)
Other epidemiologists and testing experts echoed the FDA’s warning and said testing guidance should not change until there is more data.
“There’s a lot of work under the hood that has to be done for these companies to pivot to a new sampling method,” said Albert Ko, an infectious-disease physician and epidemiologist at the Yale School of Public Health.
While agreeing that adding the throat swab “has some intuitive rationale,” Yuka Manabe, who runs the Center for Innovative Diagnostics for Infectious Diseases at Johns Hopkins University, emphasized that it is “not the way the tests were designed to be used.”
At this point in the pandemic, Manabe’s recommendation for testing is simple: “You should use at-home tests as the instructions for use tell you to use them,” she said.
Jason J. LeBlanc, director of virology, immunology, and molecular microbiology for Nova Scotia Health in Canada, said that while researchers there validated a paired collection process earlier in the pandemic, he wouldn’t recommend adding a throat swab to antigen tests that haven’t been validated using that method.
“This is an interesting topic, but requires careful investigation and any test differing from manufacturer claims need to be rigorously validated before implementation,” LeBlanc said.
Introducing a sample collected from the throat could negatively affect test performance, according to Matthew J. Binnicker, the director of clinical virology at the Mayo Clinic in Rochester, Minn. “I don’t know what that false positive rate becomes with a throat swab included in the mix,” he said.
“There may be other bacteria or viruses or inhibitors in the throat that could cause the test to perform differently than it would from a swab in the nose,” Binnicker added. “I know it sounds like it should be exactly the same, but in some certain circumstances there may be subtle differences.”
On Twitter, Mina, the testing expert who has supported adding a throat swab, noted that while the strategy does “likely improve sensitivity,” it “may potentially cause a slightly greater number of false positives.” He recommended not eating or drinking 30 minutes before swabbing.
Ko said people who are trying to get more accurate results from their rapid tests should think beyond the swab debate. “We can get hung up on what sample, which part of the nose or the mouth or whatever,” he said, “but probably the biggest driving issue about how well these tests work is when you take it and how you take it.”
A single coronavirus test — antigen or PCR — is “only giving you a snapshot of what’s happening that day,” Ko said. If people really want to be certain that they aren’t infectious, he said, they should be testing frequently. However, he acknowledged that widespread difficulties finding tests and limited access to affordable options are barriers to this approach.
With many Americans feeling as though they’re navigating this phase of the pandemic with more questions than answers, Ko called on the testing industry and the FDA to work quickly and produce the robust scientific evidence necessary to help guide public recommendations.
But Feigl-Ding said there may not be time for that. “This is one of those hallmark moments where I think federal regulators are behind the curve on the science and on the precautionary steps,” he said. “There is the official [emergency use authorization], and then there is what is likely to find more cases and save more lives.”