A pilot feasibility study on SARS-CoV-2 detection method based on nasopharyngeal lavage fluid

Frezza, D.; Fabbris, C.; Franz, L.; Vian, E.; Rigoli, R.; De Siati, R.; Emanuelli, E.; Bertinato, L.; Boscolo Rizzo, P.; Spinato, G.

Objective. Nose and nasopharyngeal swab is the preferred and worldwide accepted method to detect the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) within the nose and nasopharynx. This method may be linked with possible difficulties, such as patient discomfort or complications. This paper shows a pilot study of SARS-CoV-2 detection with nasal and nasopharyngeal lavage fluids. Methods. Nasal lavage fluid was collected from patients who were submitted to SARS-CoV-2 screening test, due to a preceding positive rapid antigen test. A control group was enrolled among healthcare professionals whose nasopharyngeal swab tested negative. Nasal lavages were performed using isotonic saline solution injected through a nasal fossa. Both lavage fluid and traditional nasopharyngeal swab were analyzed by real time PCR and antigenic test. Results. A total of 49 positive subjects were enrolled in the study. Results of the analysis on lavages and nasopharyngeal swabs were concordant for 48 cases, regardless of the antigenic and molecular test performed. Real time PCR resulted weakly positive at swab in one case and negative at lavage fluid. Among the control group (44 subjects) nasopharyngeal swab and lavage fluid analyses returned a negative result. Sensitivity of the molecular test based on nasal lavage fluid, compared to traditional nasal swab, was 97.7%, specificity was 100%, and accuracy was 98.9%, with high agreement (Cohen k, 0.978). Conclusion. Nasal and nasopharyngeal lavages resulted to be highly reliable and well tolerated. A larger series is needed in order to confirm these results. This approach may potentially represent a valid alternative to the traditional swab method in selected cases.