The first challenge of a quick COVID-19 home self-test is getting a challenge. But once you’ve had the test, there are growing questions about which body part you should swab for the most accurate and reliable results. Your nose? Throat? Mother? What about your saliva?
All self-tests authorized by the U.S. Food and Drug Administration (FDA) are validated with nasal samples only. But recent news about the fact that Omicron tends to cause sore throat, and a small one research found that swabs collected in the throat could detect the presence of the virus earlier than samples collected in the nose, which has led to a growing number of online questions about people whether a person should pick their throat instead of their nose when using the rapid self-test. In the UK, some test kits include instructing people to first pick their throat and then their nose for the most sensitive readings.
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Here’s what we know so far about the different ways to get a COVID-19 rapid test sample and how effective they are.
What we know about cotton swabs
In the US, the official word is nose picking which works well for quick tests. The FDA has authorized the tests based on studies showing that swab samples are effective for detecting markers of SARS-CoV-2, and manufacturers of rapid at-home antigen tests also stress. that their kits are designed and most accurate for prototyping. A spokesman for Abbott, which makes the popular BinaxNOW kits, said the nasal swab test was 95.6% sensitive at detecting the virus in humans within seven days of being available. symptoms, when they are most contagious. Siemens, received most recent authorization for the over-the-counter rapid test, declined to comment on the matter of throat picking and nose picking. BD, another test kit maker, also declined to comment except to say its test “is not authorized for use with cotton swabs or saliva samples”.
Some recent evidence also points to the effectiveness of this approach. Researchers at the University of California, San Francisco (UCSF) reported the results of a research compare nose picking done with a home test kit with a gold standard PCR test that requires deeper nasopharyngeal swabs performed by medical professionals. They found that home swabs of the anterior part of the nose performed almost as well on PCR tests.
They published their findings on a preprint server for scientific papers, so the results have not been peer-reviewed. But the large number of participants and the verification provided by PCR tests suggest that these results are reliable.
The study involved 731 people who went to a community trial and free vaccination site run by UCSF, Chan-Zuckerberg Biohub, the Latino Task Force, and the San Francisco Department of Public Health. Participants who agreed to participate in the study had their noses swabbed four times by a medical professional: once in each nostril with Abbott’s BinaxNOW rapid antigen test swab, and once in each nostril with a longer PCR swab. The results are compared for two different test methods. Compared to the PCR test, the rapid test is 95% sensitive in detecting Omicron cases when people are highly infectious and have high virus levels; As expected, the tests were less sensitive in reporting positivity to lower levels of virus.
Those results provide reassurance that home tests can indeed detect which people are infected with the Omicron variant. Because the results correlate well with PCR results, they also support that the nose is a good place to collect samples for testing.
The team is planning to test people by taking samples from both their throat and nose with a home kit in the coming days and compare those results.
Why do people care about throat swabs?
That may involve a changing understanding of how specifically Omicron moves through the human body when it infects humans and where it prefers to reside and establish its virus replication hub. As a respiratory virus, SARS-CoV-2 infects people through the nose and mouth by droplets containing the virus that can travel through the air and also pass from person to person via certain surfaces. While previous versions of the virus concentrated relatively quickly in the lungs – burrowing into the tissues there, multiplying and potentially causing serious and life-threatening breathing problems – studies show Omicron prefers nose and throat. (In fact, one of the hallmark symptoms of Omicron is a sore throat.) Some early research has also shown that the virus can start in the throat and move into the nasal passages, meaning that throat picking may yield positive results in infected people earlier than nose picking.
“Based on the pathogenesis of the disease, we are seeing hundreds of people get sick with COVID-19 [in whom sore throats] very prominently with Omicron,” said Dr. Diane Havilr, head of the HIV/AIDS Division at UCSF and lead author of the study. “That’s different from what we’ve seen with all the variants before, so it would make sense that the virus levels were higher in the oral and nasal samples. It is certainly justifiable. ”
However, the FDA has not authorized any at-home self-testing with throat swabs and has warned of the potential dangers of placing swabs near the throat. “When it comes to COVID-19 rapid antigen tests at home, those swabs are for your nose, not your throat,” the agency said recently. posted on Twitter. The warning came as some people started swabbing their throats with home kits after reading about other countries where throat swabs are more common and about how to extrapolate from some learn suggested that saliva samples examined by PCR could provide reliable, or even more accurate, results than deep nasal samples used for PCR.
Does the saliva test work for rapid COVID-19 testing?
Havilr’s study also included results from the use of cheek swabs, which were “less effective” than nasal samples. Cheek samples examined by both rapid tests and PCR miss a significant number of positives, with single-digit sensitivity.
That’s not to say the saliva test isn’t helpful. While cheek samples contain some saliva, saliva tests are designed differently than rapid self-tests, and the FDA has not yet authorized any COVID-19 test that is entirely self-administered with saliva. Test kits are available that allow people to collect saliva at home, but they must send the sample to a lab. The technicians then use specific procedures to detect the virus and remove other components in the saliva that could confound the results.
Key point
It remains an open question as to whether throat swabs, especially in the Omicron-dominated context, should replace cotton swabs in at-home tests. If throat swabs could detect Omicrons earlier, that would be one day earlier than the day when an infected person could isolate and limit the spread of the virus. However, some experts, including throat specialists, agree with the FDA about the potential dangers and note that people can harm themselves if they don’t pick properly, in when others feel the risk isn’t great enough to discourage people from trying it (after watching a video or getting some instructions.)
“I pick my own throat and nose for the best sensitivity when using over-the-counter tests at home,” says Dr. Michael Mina, chief scientific officer at eMed and formerly the Harvard TH Chan School of Public Health. know. , in a recent virtual Q&A session at Electronic consumer display. “But I realized I did it at my own risk when I left the label.”
Gigi Gronvall, a senior scholar at the Johns Hopkins Center for Health Security at the Hopkins Bloomberg School of Public Health, also found little harm in throat swabbing. “It’s a very low-risk trial, as long as people watch it online,” she said video that might help.
However, the data to date seem to suggest that taking that risk is unnecessary. If nasal swabs were fairly comparable in sensitivity to PCR in finding viruses, they would be a reliable way to test for COVID-19. A positive rapid test likely indicates that the person has COVID-19, but the results need to be confirmed with a PCR test. A negative test should be corroborated by another rapid test a day or so later.
