For Coronavirus Testing, the Nose May Not Always Be Best

In the past two years, a coronaviruses has often required probing the nose. Health care workers have inserted small needles into Americans' noses, while at- home test kits have asked us to twirl our double-nostrils.

The traditional approach to diagnose respiratory infections is to go after the nose, according to Dr. Donald Milton.

The spread of the Omicron variant and questions about the sensitivity of at- home tests have renewed a debate over whether the best way to detect the virus is to sample the mouth.

The first place the virus shows up is in your mouth and throat. The approach we are taking to testing has problems.

Some research suggests that collecting saliva or swabbing the inside of the mouth could be used to identify people who have been exposed to the virus earlier.

The data shows that saliva-based tests have limitations of their own, as the science is still evolving. Many labs are not set up to process saliva, and the at- home tests that are authorized for the United States are not available there.

The saliva skeptics acknowledge that oral specimen have some unique advantages. With Omicron on the march, some experts say that testing companies, labs and federal officials should be working more quickly to determine the best sample sites and types for the virus.

Anne Wyllie, a microbiologist at the Yale School of Public Health, is one of the developers of the P.C.R. testing protocol, called SalivaDirect. Many labs and governments are fixated on a certain sample type or a certain test and don't make the necessary adjustments to their testing programs.

The image is.

saliva collection kits are being assembled at a facility in Utah.

saliva testing began in the early months of the Pandemic. They wanted 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. People could simply spit saliva into a tube and give it to someone for processing.

saliva testing was not a reliable way to detect infections.

saliva was not the gold standard sample, that it wasn't the most sensitive sample, and there were concerns initially.

By the fall of 2020, dozens of studies had shown saliva to be a good sample for testing.

Dr. Wyllie said that there is a growing body of evidence that saliva performs well when it is collected and processed correctly.

saliva samples may be the best way to detect infections early, as evidence shows that the virus tends to appear in saliva before it builds up in the nose.

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. result. According to the study, more virus began to accumulate in the nose after that.

The Food and Drug Administration has approved many saliva-based P.C.R. tests, which are popular for screening students in schools.

Viva has turned out to be a valuable specimen type, and one that has been advocated as a primary testing sample.

The Omicron variant appears to replicate more quickly in the upper respiratory tract and has a shorter incubation period than earlier versions. Experts said that any testing method that can detect the virus earlier is valuable.

Omicron has changed the testing game because of how quickly the virus replicates and how quickly it spreads, according to Dr. Robby Sikka, who chairs the Covid-19 Sports and Society Working Group. Both Dr. Sikka and Dr. Wyllie are board members for SalivaDirect.

Omicron may be better at replicating in the cells of the mouth and throat than other variations have been.

A team of South African researchers recently found that saliva samples were better at detecting the Delta variant than nasal swabs. The study has not yet been reviewed by experts.

There is more research that needs to be done, and a new study conducted at a San Francisco testing site during an Omicron surge was not very encouraging. Only two of the 22 people who tested positive for a rapid antigen test were positive when their inner cheeks were tested. The scientists are looking at whether throat swabs perform better.

There are also trade-offs. The nose may be a better place to detect the virus later in the course of an illness.

The researchers at the California Institute of Technology found that the virus rose to higher levels in the nose after spiking first in saliva. The results suggest that tests like P.C.R. may be able to pick up infections in saliva days earlier than they do in nasal swabs.

Some experts said the data on saliva is still mixed.

There are a few studies that are very interesting, said Dr. Mary K. Hayden, an infectious disease doctor and clinical microbiologist at Rush University Medical Center in Chicago.

For years and years and years, research has shown that the best way to detect respiratory viruses is with a nasopharyngeal specimen.

Scientists have practical concerns as well. Joseph DeRisi, a biochemist at the University of California, San Francisco, who is a president of the Chan Zuckerberg Bio Hub, said that the mouth is more of an uncontrollable environment than the nose. Did you drink a Coke before the test? It will be different. Those things matter.

When patients are sick and dehydrated, saliva can be difficult to work with.

Different approaches may be required. For people who have had symptoms for several days, saliva may be the best choice, while nasal swabs may be the best choice for large-scale screening. He said that they need to get the right test into the right places.

In Britain, some at- home tests require a saliva sample from the throat and nose.

The image is.

Instructing a resident of Davis, Calif., how to take a saliva sample for a Covid P.C.R. test.

Adding more sites will give you an edge.

If test manufacturers want to add saliva samples or throat swabs, they will need to submit the data to regulators. The acting commissioner of the F.D.A. said at a Senate hearing on Tuesday that manufacturers might have to modify their tests to accommodate larger throat-specific samples.

It is not clear if any of the major at- home testing companies have plans to do so. John M. Koval is a spokesman for Abbott Laboratories. The test is only indicated for use in the nose.

Scientists who were convinced of saliva's potential were reluctant to recommend it to people for tests that are not authorized for that purpose. The F.D.A. warned against this. Scientists said that the mouth's biochemistry is different from the nose's and may affect the test results.

It is not easy to say, "Hey, just use a rapid antigen for saliva."

The experts hoped that laboratories, test manufacturers and regulators would quickly evaluate whether any currently available tests might perform better on other sample types.

Scientists said that the country will be well-served by having a wide variety of testing options and the ability to switch between them.

Flexibility in our testing systems is needed for future Pandemics.

Aina J. Khan reported from England.