PCR of Gargle Lavage Samples as Effective as Nasopharyngeal Swabs to Identify SARS-CoV-2 Infection, Finds Study

Twenty-six subjects from a cohort of 80 tested positive for SARS-CoV-2 via nasopharyngeal swab, and all 26 tested positive using gargle lavage (mouthwash), according to new research.

The detection method for testing samples used in this study by researchers from University of Konstanz (Konstanz, Germany) was the highly sensitive real time polymerase chain reaction (RT-PCR). Nasopharyngeal swabbing, currently the gold standard for collecting samples for COVID testing, has a low rate of acceptance due to the discomfort of having a nasal passage swabbed.

“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,” said corresponding author Christof R. Hauck, PhD, professor of cell biology, Faculty of Natural Sciences, Department of Biology, University of Konstanz, Germany.
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,” said Dr. Hauck. “We usually sent the patients with the gargle solution and sampling container outside.” There, they gargled in front of a window, observed by a physician’s staff member. Thus, “we need not expose trained personnel to the danger of taking samples from so many potentially infected people.”

Study subjects had typical respiratory symptoms or known contact with infected persons. Each received both a nasal swab administered by a professional health practitioner, “which was needed for the regular diagnostic procedure, and each self–performed a gargle lavage,” said Dr. Hauck. “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.”

“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,” said Dr. Hauck.

“By finding complete congruence of results obtained with paired samples of a sizeable patient cohort, our results strongly support the idea that the painless self-collection of gargle lavage provides a suitable and uncomplicated source for reliable SARS-CoV-2 detection,” said Dr. Hauck.

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University of Konstanz