The Atlanta Journal-Constitution
To swab or not to swab
Health experts disagree on the efficacy of adding a throat swab during your at-home COVID-19 test.
As if there hasn’t been enough confusion about what health advice Americans should follow during the coronavirus pandemic, some experts are squaring off about how to employ an important weapon in the battle against the highly transmissible omicron variant: at-home rapid antigen tests. On one side are well-regarded experts who argue that swabbing your throat
in addition to your nose may increase the chances that a home test can detect omicron.
On the other side are similarly well-regarded experts, including those at the Food and Drug Administration, who urge Americans to avoid experimenting with kits that were developed and tested using only nasal swabs.
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 detect the omicron variant, some “may have reduced sensitivity,” citing an early finding from ongoing performance evaluations.
People have posted anecdotal stories of having coronavirus symptoms and testing negative when using a rapid test kit as instructed (only swabbing their noses). But when they swabbed their throats as well as their noses, they said, the test came back positive.
Some prominent experts also have started recommending the additional throat swab.
What they’re saying
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.”
Eric Feigl-ding, an epidemiologist and senior fellow at the Federation of American Scientists, agreed. “Omicron is very different from all other variants,” he tweeted. “We need to adapt to changing testing strategies.”
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 the 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. Another recent paper reported data showing that viral loads peaked in saliva one to two days before they peaked in tests that used nasal swabs.
Testing options
Those research papers were released as preprint articles, meaning formal peer review of the work has not been completed.
Feigl-ding also noted that other countries, such as Canada and the United Kingdom, have authorized testing options that use throat swabs along with nasal swabs.
“This is a precautionary approach,” Feigl-ding 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 COVID19 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 last week.
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.)
Work needs to be done
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.”
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.”
Snapshot of that day
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.”