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For Coronavirus Testing, the Nose May Not Always Be Best - The New York Times
Jan 14, 2022 2 mins, 53 secs
As Omicron spreads, some experts are calling for a switch to saliva-based tests, which may detect infections days earlier than nasal swabs do.

Health care workers have inserted slender swabs deep into the recesses of Americans’ nasal passages, while at-home test kits have asked us to master the shallow double-nostril twirl.

But the rapid spread of the Omicron variant, and questions about the sensitivity of at-home tests, have rekindled a debate over whether the best way to detect the virus is to sample a different site: the mouth.

Collecting samples of saliva, or swabbing the inside of the mouth, could help identify people who are infected with the virus days earlier than nasal swabs do, some research suggests.

Many labs are not currently set up to process saliva, nor are the at-home antigen tests available in the United States authorized for it.

And with Omicron on the march, some experts say that testing companies, labs and federal officials should be working more urgently to determine the best sample sites and types for the virus.

They were eager to find a testing method that would be more comfortable than the deep nasopharyngeal swabs that were the standard at the time and that would not require trained health care workers or nasal swabs, both of which were in short supply.

“There were concerns initially that saliva was not the gold standard sample, that it wasn’t the most sensitive sample,” said Glen Hansen of the clinical microbiology and molecular diagnostics laboratory at Hennepin County Medical Center in Minnesota.

Evidence also emerged that the virus tended to appear in saliva before it built up in the nose, suggesting that saliva samples might be the best way to detect infections early.

Milton and his colleagues recently found that in the three days before symptoms appear and the two days after, saliva samples contained about three times as much virus as nasal samples and were 12 times as likely to produce a positive P.C.R.

Any testing method that can reliably detect the virus earlier is particularly valuable, experts said.

“I think Omicron has really changed the testing game because of how quickly the virus replicates and how quickly it spreads,” said Dr.

A team of South African researchers recently found that while nasal swabs performed better than saliva swabs when detecting the Delta variant, the opposite was true for Omicron.

Of the 22 people who tested positive on a rapid antigen test using standard nasal swabs, only two tested positive when their inner cheeks were swabbed.

tests, may be able to pick up infections in saliva days earlier than they do in nasal swabs, but that less-sensitive tests, like antigen tests, might not.

The data on saliva are still mixed, some experts noted.

For people who have had symptoms for several days, nasal swabs might be a good choice, while saliva might be best suited for the large-scale surveillance screening of asymptomatic people, Dr.

In Britain, some at-home tests require swabbing both the throat and the nose, an approach that may be worth pursuing, experts said.

But if test manufacturers want to add saliva samples or throat swabs, they will need to validate their tests with those samples and submit the data to regulators.

Koval, a spokesman for Abbott Laboratories, which makes rapid antigen tests.

But experts said they hoped that laboratories, test manufacturers and regulators would move swiftly to evaluate whether any currently available tests might perform better on other sample types

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