Noninvasive Saliva Tests for COVID-19 as Effective as Nose, Throat Swabs

• Researchers say new saliva tests are nearly as accurate as throat and nasal swabs to detect COVID-19.
• They note that the tests are easier and less invasive than other exams, factors that could help increase the number of COVID-19 tests.
• Some at-home tests require a prescription, and some need to be sent to labs while others don’t.

What a negative result means

The Food and Drug Administration (FDA) says that a negative testTrusted Source means COVID-19 was not found in your test specimen.

While this typically means you’re free of the novel coronavirus, it’s important to remember that no currently available test is 100 percent accurate.

“It is possible for a test to give a negative result in some people who have COVID-19 (that is, a false negative),” states the Centers for Disease Control and Prevention (CDC)Trusted Source. “Discuss your symptoms and test results with your healthcare provider to determine if you need follow-up testing.”

Kumar said false negatives can be a result of factors such as test accuracy but also timing of the test and sample collection.

Kroll advises testing to be performed after a requisite amount of days, “or the test will provide a false negative result and this same concept holds true with healthcare facility testing for coronavirus,” he said.

“Patients should not test before 5 to 7 days after exposure — even with symptoms — and they should consider themselves potentially infectious until that time and until proven to be COVID-19 negative by a home test,” Kroll said.

“It is best to err on the side of caution to reduce the risk of spread to others,” Kumar added.

“If an individual has symptoms suggestive of COVID-19 or a known exposure to COVID-19, it is important to discuss with your healthcare provider to determine if you need follow-up testing,” Kroll said.

Factors impacting testing accuracy

Kroll said many things can interfere with testing results.

He said that multiple interfering agents have been tested and don’t appear to impede the accuracy of saliva testing.

These include decongestant nasal sprays, steroid nasal sprays, sore throat lozenges, blood, toothpaste, and mouthwash.

But possible false results could come from contamination with food and other substances, Kroll said.

“Smoking tends to dry the mouth and might reduce the ability to produce an adequate specimen,” he said. “It is also theoretically possible that alcohol could denature the viral RNA so that it cannot be amplified and detected in the test.”

“Appropriate precautions for potentially interfering substances and proper self-collection of samples is necessary,” Kroll noted.

The good news, Kumar said, is the at-home tests come with easy-to-follow instructions. This can help reduce margins of error.