Comparative analysis of the naso/oropharyngeal swab and oral bio-fluid (whole saliva) samples for the detection of SARS-CoV-2 using RT-qPCR

Abstract

Context: The Corona Virus Disease 2019 (COVID-19) is a contagious disease caused by the novel Coronavirus (2019-nCoV) and was declared a pandemic disease by the World Health Organization (WHO) in March 2020. The nasopharyngeal and the oropharyngeal swabs are being taken during the screening procedure. However, the virus is also present in the oral bio-fluid and hence it could be a potential tool for screening COVID-19 cases.

Aim: The aim of the present study was to test the accuracy of whole saliva as a diagnostic specimen in COVID-19.

Settings and design: This cross-sectional, analytical study was conducted on out-patients visiting the COVID-19 hospital.

Methods and material: The whole saliva and the nasopharyngeal/oropharyngeal samples from 309 COVID-19 suspected patients were collected and subjected to RT-PCR analysis.

Statistical analysis used: The paired t test was used to compare the measured variables (C_T values) between the saliva and the swab samples. The positive predictive value (PPV), negative predictive value (NPV), the sensitivity, and the specificity of the tests were calculated for the saliva sample.

Results: The saliva and swab results revealed a similar result (ties) in 86.73% of the samples. The sensitivity and the specificity between the swab and saliva samples were 40% and 96.85%, respectively. The positive predictive value of the saliva sample was 73.3%.

Conclusions: The sensitivity of whole saliva when compared to the swab samples is low. Large sample studies are needed to validate the role of saliva as a diagnostic tool in COVID-19.

Keywords: Biological marker; COVID-19; SARS-CoV-2; oral bio-fluid; whole saliva.