The reliability of saliva for the detection of SARS-CoV-2 in symptomatic and asymptomatic patients: Insights on the diagnostic performance and utility for COVID-19 screening

Current literature has focused on testing saliva in symptomatic patients, and little information is available regarding saliva performance in asymptomatic severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection. We compared paired saliva and nasopharyngeal swabs (NPS) collected from 33 symptomatic and 12 asymptomatic known SARS-CoV-2-positive patients. Saliva had an overall sensitivity of 59%, a specificity of 95%, and a negative predictive value of 98%. Saliva demonstrated higher sensitivity in symptomatic (80%) vs. asymptomatic individuals (36%) (P = 0.006), and in high-risk (symptomatic, febrile and/or with comorbidities) (82%) vs. low-risk (asymptomatic, afebrile, and no comorbidities) (22%) patients (P = 0.0002). Cycle threshold (Ct) values in NPS specimens were higher in saliva-negative vs. saliva-positive cases (P = 0.02 and <0.001). Overall, these findings show that despite saliva's low sensitivity in asymptomatic SARS-CoV-2 infections, it can detect infections with lower Ct values and a potentially higher chance of viral transmission. Additional studies are warranted to fully evaluate saliva as a screening test for coronavirus disease-2019.