For Coronavirus Testing, the Nose May Not Always Be Best

Saliva additionally has trade-offs. While the virus seems to construct up in saliva early, the nostril could also be a greater place to detect it later in the middle of an infection.

Researchers on the California Institute of Technology discovered that while the virus usually spiked first in saliva, it in the end rose to increased ranges within the nostril. Their outcomes recommend that extremely delicate assessments, like P.C.R. assessments, could possibly choose up infections in saliva days sooner than they do in nasal swabs, however that less-sensitive assessments, like antigen assessments, may not.

The information on saliva are nonetheless blended, some consultants famous.

“There are these few studies that I have found really very interesting,” mentioned Dr. Mary Ok. Hayden, an infectious illness physician and scientific microbiologist at Rush University Medical Center in Chicago.

But Dr. Hayden mentioned she was decoding the new research cautiously as a result of “for years and years and years,” analysis has recommended that nasopharyngeal specimens are greatest for detecting respiratory viruses.

Some scientists additionally have sensible considerations. The mouth is “a little more of an uncontrolled environment compared to the nasal passages,” mentioned Joseph DeRisi, a biochemist on the University of California, San Francisco, who’s a president of the Chan Zuckerberg Biohub and an creator of the cheek swab paper. “Did you drink a Coke right before you took the test? The pH will be different. And those things matter.”

Saliva might be “viscous and difficult to work with,” particularly when sufferers are sick and dehydrated, Dr. Marie-Louise Landry, director of the scientific virology laboratory at Yale New Haven Hospital, mentioned in an e-mail.

Ultimately, completely different approaches could also be required in several circumstances. For people who have had signs for a number of days, nasal swabs is likely to be a sensible choice, while saliva is likely to be greatest suited to the large-scale surveillance screening of asymptomatic people, Dr. Hansen recommended. “We need to get the right test into the right places,” he mentioned.

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