Performance of Saliva Specimens for the Molecular Detection of SARS-CoV-2 in the Community Setting: Does Sample Collection Method Matter?

Abstract

Data on the performance of saliva specimens for diagnosing coronavirus disease 2019 (COVID-19) in ambulatory patients are scarce and inconsistent. We assessed saliva-based specimens for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by reverse transcriptase PCR (RT-PCR) in the community setting and compared three different collection methods. This prospective study was conducted in three primary care centers. RT-PCR was performed on paired nasopharyngeal swabs (NPS) and saliva samples collected from outpatients with a broad clinical spectrum of illness. To assess differences in collection methods, saliva specimens were obtained in a different way in each of the participating centers: supervised collection (SVC), oropharyngeal washing (OPW), and self-collection (SC). Pairs of NPS and saliva samples from 577 patients (median age, 39 years; 44% men; 42% asymptomatic) were collected and tested, and 120 (20.8%) gave positive results. The overall agreement with NPS results and kappa coefficients (κ) for saliva samples obtained by SVC, OPW, and SC were 95% (κ = 0.85), 93.4% (κ = 0.76), and 93.3% (κ = 0.76), respectively. The sensitivities (95% confidence intervals [95% CI]) of the saliva specimens ranged from 86% (72.6% to 93.7%) for SVC to 66.7% (50.4% to 80%) for SC samples. Sensitivity was higher for samples with lower cycle threshold (CT) values. The best RT-PCR performance was observed for SVC, with sensitivities (95% CI) of 100% (85.9% to 100%) in symptomatic individuals and 88.9% (50.7% to 99.4%) in asymptomatic individuals at CT values of #30. We conclude that saliva is an acceptable specimen for the detection of SARS-CoV-2 in the community setting. Specimens collected under supervision perform comparably to NPS and can effectively identify individuals at higher risk of transmission under real-life conditions.