Saliva tests for Covid-19 could be at least as accurate — possibly more so — than the commonly used nasal swab tests in screening for the coronavirus, new research from Yale University shows.
The researchers said their findings suggest that saliva samples could be used for at-home coronavirus tests on a large scale nationally.
Released Wednesday, the study hasn't been submitted for review by peers yet, and further validation of those findings might be needed before saliva-based tests are rolled out in a big way.
The study comes on the heels of approval by the Food and Drug Administration of new saliva tests for Covid-19, and amid intense pressure to increase the number of tests for coronavirus performed in the United States each day.
Increased testing for coronavirus, coupled with contact tracing of infected people, is seen as essential by public health officials to ensure that Americans can safely return to work and social events without triggering a second wave of coronavirus infections that could overwhelm local health systems.
The study notes that testing that relies on long nasal swabs has been "the current gold standard for Covid-19 diagnosis."
But the authors added there has been a need to come up with new types of tests because of the "low sensitivity" seen in some test results using swabs.
Another problem with relying on nasal swabs, they noted, is the risk of exposing health-care workers to infected people because of the need to have close contact during the sample collection. They also said there was a global shortage of swabs and personal protective equipment.
Saliva is a promising candidate for coronavirus tests because "collection is minimally invasive and can reliably be self-administered," the authors wrote. And "saliva has exhibited comparable sensitivity to nasopharyngeal swabs in detection of other respiratory pathogens," they added.
The study compared the saliva-based test results against tests of nasal swab samples from confirmed Covid-19 patients, as well as self-collected samples from health-care workers.
The authors said they collected 44 samples from Covid-19 study participants and also tested 121 self-collected saliva or nasal swabs from health-care workers.
"When we compared SARS-CoV-2 detection from patient-matched nasopharyngeal and saliva samples, we found that saliva yielded greater detection sensitivity and consistency throughout the course of infection," the authors wrote.
"Furthermore, we report less variability in self-sample collection of saliva," the authors wrote.
"Taken together, our findings demonstrate that saliva is a viable and more sensitive alternative to nasopharyngeal swabs and could enable at-home self-administered sample collection for accurate large-scale SARS-CoV-2 testing."
The study was published the day after the first at-home coronavirus test kit was approved by the U.S. Food and Drug Administration.
The test, developed by Labcorp, uses nasal swabs that can collect samples more easily than the longer swabs.
Last week, the FDA granted emergency use authorization for a coronavirus test relying on saliva samples that was developed by a Rutgers University-backed entity.
The newly authorized test, which requires a person with coronavirus symptoms to spit into a cup, could increase the number of Covid-19 screenings by up to 10,000 tests per day, according to Rutgers.
But the new study from Yale could support and increase reliance on saliva tests, especially if nasal swabs continue to run low.
Dr. Mike Pellini, managing partner of health venture firm Section 32, and a diagnostics specialist, said he was "excited by this progress" shown in the new study.
"We need to have more solutions to solve the current challenges with swabs," said Pellini.
"Given the newness of the approach coupled with the potential for its broad utility, I'd certainly like to see additional published validation study to confirm the results."
Infectious disease specialist Dr. Tom Moore told CNBC last week that the potential impact from saliva-based tests like the one developed by Rutgers being widely available is "enormous."
"The release of any reliable test, expanded capacity of tests or introduction of new tests ... will go a really long way toward curbing the pandemic," said Moore, a Wichita, Kansas, physician who previously served on the board of the Infectious Diseases Society of America.
The research was partially funded by Yale Institute for Global Health. The study's authors didn't disclose their full funding but said that the funding sources "had no role in study design, data collection, data analysis, data interpretation, or writing of the report." No funds from any company were used to pay for the saliva study, the researchers confirmed to CNBC.