Saliva as a Non-Invasive Sample for Molecular Detection of SARS- CoV-2

Abstract

Objective: To evaluate the Saliva specimen as a non-invasive sample for molecular detection of SARS-CoV-2 compared with Nasopharyngeal Swab.

Study Design: Cross-sectional study.

Place and Duration of Study: Department of Virology Armed Forces Institute of Pathology (AFIP), Rawalpindi, in Oct 2020.

Methodology: Forty-eight patients were included in this study from SARS-CoV-2 Outdoor Clinic in Pak Emirates Military (PEMH), Rawalpindi. Out of 48 patients, 28 known SARS-CoV-2 positives by Real-Time Polymerase Chain Reaction (RT-PCR) and 20 known SARS-CoV-2 RT-PCR negative patients were included in this study. Paired samples of Nasopharyngeal swabs and Saliva samples were collected from forty-eight patients. Samples were transported to Virology Department AFIP in Viral Transport Medium (VTM) and subjected to SARS-CoV-2 RT-PCR simultaneously. The sensitivity and specificity of the Saliva specimen for SARS-COV-2 RT-PCR were compared with Nasopharyngeal Swab.

Results: A total of 48 patients were included in this study, of which 28 (58%) patients were positive for SARS-CoV-2 on NPS by RT-PCR. Among the 28 positive cases, 18 (64.3%) were positive by RT-PCR using saliva specimens. The sensitivity and specificity of saliva specimens compared with NPS were 64.3% and 95%, respectively.

Conclusion: Saliva specimen has much lower sensitivity as compared to NPS in our study. Therefore, it cannot be implemented for the diagnosis of COVID-19 as it can compromise the results of a highly sensitive test like RT-PCR.