A new study suggests that rapid COVID-19 tests that use nose swabs alone might not pick up Omicron in the early days of infections.
A small study from a group of US researchers, published Tuesday, found that rapid tests for Omicron didn't detect it for one to two days after initial infections. The researchers said that four participants spread infections before their tests showed positive.
The study, which hasn't yet been published in a medical journal or scrutinized by other scientists in a peer review, adds to emerging evidence that throat and nose swabs can be used together to detect Omicron.
The FDA said in a statement Tuesday that rapid tests should be used as per their instructions because of safety concerns about self-collection of throat swabs. According to the FDA, a trained healthcare provider can collect throat swabs.
30 people from five different places were involved in the study. The study authors said that all of the participants were fully-vaccinated and had received a booster dose.
The researchers said that in a sub-group of five people, the virus particles in saliva peaked one to two days before they were detected.
Dr Michael Mina, a former associate professor of epidemiology at the Harvard Chan School of Public Health, said of the findings: "Many reports show saliva comes up earlier and with Omicron there have been many anecdotes that throat swabs are turning positive before nasal swabs."
He said the study suggests people become infectious when saliva turns positive.
If not by the FDA, Mina has advocated testing both nose and throat for a rapid test, regardless of the test instructions.
In the UK, users are told to take a saliva sample from their nose and throat.
Dr Peter M B English, a consultant in communicable disease control, said that the study findings were confirmation that nose swabs alone do not effectively detect the Omicron variant. The instructions for the test kit should be changed immediately.
It wasn't clear from the data available how much earlier a saliva test would be able to be compared to a nasal test.
The chief of the infectious diseases division of New York-Presbyterian/Weill Cornell Medical Center told Today on Wednesday that he couldn't recommend people use throat swabs.
He said that the tests have been authorized in a different way. Don't take matters into your own hands. We need to wait to see if any of these tests will be valid to do a throat swab.
If an at- home rapid test is positive, then you should believe it. If it's negative, you should get a lab test to find out if you have symptoms of COVID-19.
A study from South Africa showed using throat and nose samples to detect Omicron infections, but only a small amount of Delta infections.
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