Simple mouthwash test for COVID just as accurate as nasal swabs

WASHINGTON — Anyone who has undergone a SARS-CoV-2 nasopharyngeal swab test knows that they aren’t exactly a pleasant experience. Despite this “brain-tickling” test being quite uncomfortable, scientists still consider it the gold standard of COVID tests. That may soon change, however. New research indicates that a gargle lavage (mouthwash) test is just as accurate as a swab assessment and a much simpler process to boot.

Among a group of 80 individuals, 26 tested positive for COVID-19 via swab testing. When that same group used a mouthwash test, the exact same 26 individuals tested positive as well. Importantly, both the nasal and mouthwash tests were of the polymerase chain reaction (RT-PCR) variety. Researchers say these tests are highly sensitive and capable of producing a result in real-time.

“Our results show that in all cases, where people were positively tested by the gold standard nasal swabbing, one could also detect the virus in gargle lavage by the same RT-PCR method,” says corresponding study author Christof R. Hauck, PhD, a professor of cell biology at the University of Konstanz in Germany, in a media release.

Even better, whereas the swab test requires medical personnel to conduct the exam and wear PPE, individuals can do the mouthwash test by themselves.

“This sampling procedure can be conducted safely in a general practitioner’s office without extra protective equipment for physicians’ staff, as the patients themselves perform the sampling,” Dr. Hauck explains. “We usually sent the patients with the gargle solution and sampling container outside.”

Mouthwash COVID test can be done at home, keeping everyone safe

All medical staff have to do is watch the patient from a window to ensure they gargle the solution and spit it back into a cup correctly.

“We need not expose trained personnel to the danger of taking samples from so many potentially infected people,” Dr. Hauck adds.

All tested subjects were either dealing with some respiratory symptoms or had come into contact with a COVID-positive individual. Everyone underwent a swab test first, and then performed the mouthwash test themselves.

“These paired samples were then transferred to the central diagnostic lab, where they were analyzed in parallel, so that the results could be directly compared,” Dr. Hauck notes.

“Besides performing diagnostics on symptomatic patients, we are involved in regular SARS-CoV-2 surveillance on our university campus, where we test people twice a week. As nasal swabbing is not very pleasant, we were looking for an alternative, and gargle lavage turned out to be highly accepted,” he continues.

The fact that both tests came to the exact same results leads the research team to conclude that “the painless self-collection of gargle lavage provides a suitable and uncomplicated source for reliable SARS-CoV-2 detection.”

The findings appear in the journal Microbiology Spectrum.