Saliva as a Viable and Simple Alternative to Nasopharyngeal and Oropharyngeal Swabs for COVID-19 Real-Time Reverse Transcriptase Polymerase Chain Reaction

Introduction: Attributable to the difficulties in specimen collection, discomfort and symptoms caused on by Nasopharyngeal Swab (NPS) and Oropharyngeal Swab (OPS) collection, and significant risk to Healthcare Workers (HCW), evaluation of an alternative specimen for the diagnosis of Coronavirus Disease-2019 (COVID-19) is required. Saliva specimen could be an alternative specimen with many advantages over NPS and OPS, however little is known about how well it performs this purpose.

Aim: To assess the efficacy of saliva as a viable and simple alternative specimen to NPS and OPS for COVID-19 Real-Time reverse transcriptase Polymerase Chain Reaction (rRT-PCR).

Materials and Methods: The present cross-sectional study was conducted in the Department of Microbiology, SGT Medical College Hospital and Research Institute, Haryana, India, from July to December 2020. A total of 60 symptomatic and 20 asymptomatic COVID-19 patients were recruited for the study and specimen viz., saliva, NPS and OPS were collected at four different sampling points i.e., on day one, five, seven and 14 after confirmation of COVID-19 rRT-PCR test positivity. Data obtained from the study was analysed and expressed as median, frequency, interquartile range and Chi-square test was done for comparison of categorical variables.

Results: Majority of the patients in symptomatic hospitalised COVID-19 patients were males 49 (81.7%) and remaining were females 11 (18.3%) and in asymptomatic group 8 (40%) were males and 12 (60%) were females. Saliva was the most sensitive specimen (74.2%), followed by NPS, Naso Oropharyngeal Swab (NOPS) with 70.8% each and OPS (65.8%) for detection of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) in symptomatic patients at four different sampling points. Comparable findings were also observed in specimens obtained from asymptomatic individuals as well. In addition, the viral load was also highest in saliva sample, as measured by Cycle Threshold (Ct) value. Across all specimen types, high viral load (lower Ct values) was observed during the early period of infection. Majority of the study participants reported discomfort during NPS and OPS collection (90% and 85%, respectively), lacrimation, sneezing and gag reflex being the most commonly reported induced symptoms.

Conclusion: In the present study, saliva could be a viable and alternate specimen for COVID-19 diagnosis due to its ease in sample collection, specimen stability and reduced risk of transmission of infection due to droplets.