Influence of Saliva Collection Method on the Detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Immunoglobulin G (IgG) Antibodies in the Saliva: A Cross-Sectional Study

Abstract

ABSTRACT Background: Although the nasopharyngeal swabs (NPS) are considered as the gold standard specimen for the clinical diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus in the coronavirus disease 2019 (COVID-19), they pose several limitations such as the high risk of exposure, discomfort to the patients, and requirement of trained healthcare professionals. Aim: This study aimed to investigate “saliva” as an alternate source and the influence of the method of saliva collection on the sensitivity of SARS-CoV-2 detection. Materials and Methods: In this cross-sectional study, patients were screened for the COVID-19 infection with NPS. Saliva was collected from the same patients by four different methods (expectoration, drooling, gargling, and using salivary swabs) and stored at 80°C. Saliva samples of the patients who were detected positive for SARS-CoV-2 were analyzed for viral load by RT-qPCR and immunoglobulin G (IgG) levels by ELISA. Results: Out of 350 patients screened, 43 patients were included in the study, which were found to be positive for COVID-19 as evidenced by RT-PCR in the NPS (positivity rate-12.2%). Expectorated saliva exhibited 78.5% sensitivity and drooling method showed 22.2% sensitivity, whereas the salivary swab and gargling method yielded 21.42% and 16.66% sensitivity, respectively. Furthermore, the sensitivity of SARS-CoV-2 detection was reduced to 18.1% and 0.0% in the saliva collected by salivary swab and gargling method above the cycle threshold value 25.0 (NPS). Conclusion: Interestingly, salivary IgG showed better concordance with the viral load as compared to the serum IgG (R20.23 vs 0.04, P = 0.044). Expectorated saliva is a better specimen as compared to the drooling, gargling, and salivary swabs for SARS-CoV-2 viral detection for the clinical diagnosis of COVID-19.