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Nasal Lavage May Be a Valid Alternative to Swab Method in SARS-CoV-2 Detection

by Linda Kossoff •

What is the feasibility and accuracy of nasal lavage as a method to collect samples from the nasopharynx for SARS-CoV-2 detection?

BOTTOM LINE

Nasal and nasopharyngeal lavages appear to be well tolerated and highly reliable in detecting SARS-CoV-2 and may be a valid alternative to the traditional swab method in selected cases.

BACKGROUND: The COVID-19 pandemic requires massive population testing, raising issues about diagnostic accuracy and large-scale sample collection feasibility. Nose and nasopharyngeal swab is currently the worldwide-accepted method for detecting SARS-CoV-2. However, this operator-dependent method requires a steep learning curve for healthcare providers, potentially affecting reliability.

STUDY DESIGN: Controlled study.

SETTING: Treviso General Hospital, Treviso, Italy.

SYNOPSIS: Researchers collected lavage fluid from 49 patients who had tested positive on their first rapid antigen test performed on a nasopharyngeal swab and had returned to a screening center to perform the confirmatory PCR-based test. A control group of 44 healthcare professionals whose nasopharyngeal swab tested negative was enrolled. For the study, each patient underwent standard nasopharyngeal swab for molecular analysis. Nasal lavages were performed, and the mixed fluids were evacuated and collected in sterile tubes. Fluid collection was well tolerated with no adverse events. Swabs and fluids were analyzed simultaneously by real-time PCR. In all subjects but one, results of the analysis on lavage fluid and traditional nasopharyngeal swab were concordant. All patients in the control group tested negative in both analyses. The SARS-CoV-2 diagnosis based on RT-PCR from lavage was observed to be feasible and accurate (specificity and sensitivity 97.7% and 100%, respectively) when compared with the gold standard PCR from nasopharyngeal swab. Authors conclude that nasal lavage may be an advantageous method to obtain samples from nasopharynx for SARS-CoV-2 detection compared to the traditional swab. They note that larger cohort studies are needed to confirm their results.

Citation: Freezza D, Fabbris C, Franz L, et al. A severe acute respiratory syndrome coronavirus 2 detection method based on nasal and nasopharyngeal lavage fluid: a pilot feasibility study. Laryngoscope Investig Otolaryngol. 2021;6:646-649.