Large parallel screen of saliva and nasopharyngeal swabs in a test center setting proofs utility of saliva as alternate specimen for SARS-CoV-2 detection by RT-PCR

BackgroundA high volume of testing followed by rapid isolation and quarantine measures is critical to the containment of SARS-CoV-2. RT-PCR of nasopharyngeal swabs (NPS) has been established as sensitive gold standard for the detection of SARS-CoV-2 infection. Yet, additional test strategies are in demand to increase and broaden testing opportunities. As one attractive option, saliva has been discussed as an alternative to NPS as its collection is simple, non-invasive, suited for children and amenable for mass- and home-testing. MethodsHere, we report on the outcome of a head-to-head comparison of SARS-CoV-2 detection by RT-PCR in saliva and nasopharyngeal swab (NPS) of 1187 adults and children reporting to outpatient test centers and an emergency unit for an initial SARS-CoV-2 screen. ResultsIn total, 252 individuals were tested SARS-CoV-2 positive in either NPS or saliva. SARS-CoV-2 RT-PCR results in the two specimens showed a high agreement (Overall Percent Agreement = 98.0%). Despite lower viral loads in saliva, we observed sensitive detection of SARS-CoV-2 in saliva up to a threshold of Ct 33 in the corresponding NPS (Positive Percent Agreement = 97.7%). In patients with Ct above 33 in NPS, agreement rate dropped but still reaches notable 55.9%. ConclusionThe comprehensive parallel analysis of NPS and saliva reported here establishes saliva as a reliable specimen for the detection of SARS-CoV-2 that can be readily added to the diagnostic portfolio to increase and facilitate testing. Key pointsComparison with nasopharyngeal swabs in a large test center-based study shows that saliva is a reliable and convenient material for the detection of SARS-CoV-2 by RT-PCR in adults and children.