Diagnostic accuracy of saliva as a specimen for detection of SARS-CoV-2 by RT-PCR

COVID-19 caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is an emerging pandemic that is rapidly spreading with more than 114 million confirmed cases and 2.5 million deaths by far. Nasopharyngeal swab (NPS) in VTM has been used as the gold standard respiratory specimen for SARS-CoV-2 reverse-transcriptase real-time PCR (rRT-PCR) tests. But now the virus can also be detected in other clinical specimens like bronchoalveolar lavage, sputum, saliva, throat swab, blood, and stool specimens.

The aim of this study was to determine the diagnostic potential of saliva as a sample in comparison to NPS for detection of SARS-CoV-2 by rRT-PCR.

A cross-sectional study was conducted among 256 paired samples (NPS and Saliva) received in the Department of Microbiology, SMS Medical College, Jaipur over a period of 2 months.

NPS from individuals were collected in a sterile tube containing Viral Transport Medium™. Before swab collection, whole saliva was collected by spitting from the suspected patient into a sterile container. Both were stored at room temperature and transferred to the diagnostic laboratory within four hours of collection where extraction was done using Perkin Elmer chemagic extractor and rRT- PCR was performed using NIV, Pune mastermix.

Sensitivity, specificity, PPV, and NPV of RT-PCR for the diagnosis of COVID-19 in saliva were 84.26%, 100%, 100%, and 54.05%, respectively. The accuracy of detection of COVID-19 by saliva samples compared to the routinely used NPS samples (considered as the standard reference) for RT PCR was 86.72%.

Our results show that saliva as a reliable sample type for SARS-CoV-2 detection.