The omicron coronavirus variant is forcing health experts and the public alike to question everything they thought they knew about COVID-19, including how to properly take at-home rapid tests to ensure an accurate result.
All rapid tests authorized for emergency use in the U.S. require a sturdy swab of your nasal cavity, though not deep enough to tickle your brain like early PCR tests.
However, a growing body of anecdotal evidence suggests you may want to throw in a throat sample, too.
“Symptoms are starting [very] early [with] omicron. This means that there is a chance the virus isn’t yet growing in the nose when you first test,” Dr. Michael Mina, a former associate professor of epidemiology at the Harvard T.H. Chan School of Public Health and chief science officer of eMed, a digital health care company, wrote on Twitter. “[The] virus may start further down. Throat swab [and] nasal may improve chances a swab picks up virus.”
The extra swab “likely improves sensitivity” of the test, Mina said, although it “may potentially cause a slightly greater number of false positives.”
Because rapid tests in the U.S. are specifically designed to read nasal samples, some potential COVID-19 carriers worry throat swabs won’t suffice, but Mina said the tests are still capable of doing their job.
Dr. Amesh Adalja, an infectious disease expert and senior scholar at the Johns Hopkins University Center for Health Security, agrees swabbing your nose and throat when taking a rapid COVID-19 test could increase its sensitivity.
“Most viruses replicate in both the nasopharynx and the oropharynx, which are anatomically contiguous, and they [cause] both nasal and throat symptoms,” Adalja told HuffPost, adding that tests for other viruses such as the flu and rhinovirus are more accurate when fed throat samples.
The omicron variant is known for causing cold-like symptoms that could affect the entire respiratory system, but the extra swab may most benefit those who have a sore throat.
“However, getting samples from both may be the best practice,” Adalja said.
Just try not to think about sharing mucous from your throat and nose.
“It’s so gross,” but “I just want to be sure it’s negative,” Dr. Michal Caspi Tal, an immunologist at Stanford University in California, told Slate.
Where and how the omicron variant replicates in our bodies could explain why throat swabs may help COVID-19 rapid tests produce more accurate results.
One early study, which has not been peer-reviewed, from the University of Hong Kong found that omicron “infects and multiplies 70 times faster” than the delta variant in the bronchi, the main airways into the lungs. Researchers say this behavior may explain omicron’s high transmissibility compared to delta.
Another non-peer-reviewed study found self-collected PCR nose swabs caught 100% of coronavirus infections caused by the delta variant, but only 86% of those caused by omicron. Meanwhile, throat swabs detected all omicron cases and just 71% of delta infections.
Nose swabs for rapid tests may also give false COVID-19 results because you aren’t sampling correctly, Dr. Purvi Parikh, an adult and pediatric allergist and immunologist with the Allergy & Asthma Network, told HuffPost.
“A person may not get enough sample to detect virus if they do the nasal test incorrectly or do not go deep enough,” Parikh told the outlet. “Whereas if you have a sore throat, likely whatever is deep in your nose has dripped down the back of your throat.”
PCR tests work by taking a small sample of coronavirus genetic material and replicating it “thousands of times so it can be more easily detected,” Johns Hopkins University School of Medicine researchers say. They require trained laboratory technicians and special equipment that only some testing facilities have.
The tests also take at least an hour — but likely longer — to process samples, and people may not receive their PCR results for days.
Rapid tests, on the other hand, come in premade kits with laboratory-produced antibodies that glue onto proteins sitting on the surface of coronavirus particles in patient samples. Anyone can complete the test, and it can be taken anywhere, offering results within 15 minutes.
“What we determined was that while the PCR test may be a better test from a clinical perspective — as it’s basically 100% accurate at detecting (the coronavirus) — the rapid antigen test appears to be better from a public health standpoint because of its ease of use, and the fact that it proved to have sufficient accuracy, specificity and reliability for detecting the coronavirus in a high-volume setting,” Dr. James Ficke, professor of orthopedic surgery at the Johns Hopkins University School of Medicine, said in a news release.
Ficke is the senior author of a study that found rapid COVID-19 tests are more effective than previously thought.
Generally, rapid antigen tests will detect higher levels of the coronavirus, meaning a positive test result may reveal a person is very contagious, experts say. But they do have higher rates of false negatives than PCR tests, which are more sensitive and catch lower levels of coronavirus in people, Dr. Robert Shmerling, an associate professor of medicine at Harvard Medical School in Boston, wrote in a Harvard blog post.
Still, “a negative result suggests there’s too little virus to infect others, at least at the time of the test,” he said.