Usability of saliva as a reliable and non-invasive sample for SARS-CoV-2 detection in Durban, South Africa

Abstract

Background Saliva has been proposed as a potential more convenient, cost-effective, and easier sample for diagnosing SARS-CoV-2 infections, but there is limited knowledge of the impact of saliva volumes and stages of infection on its sensitivity and specificity. Methods In this study, we evaluated the performance of SARS-CoV-2 testing in 171 saliva samples across different volumes (50, 100, 300 and 500ul of saliva) and at different stages of disease (at screening, day 7, 14 and 28 post SARS-CoV-2 diagnosis) from 52 mostly mild symptomatic patients. Imperfect nasopharyngeal swab samples were used as a reference. Results Overall, 52 of the 171 samples were positive, with sensitivity of 73.2% and specificity of 81.0%. The sensitivity of saliva samples ranged from 70.6% for 50µl to 83.3% for 300µl of saliva collected. The specificity values ranged between 78.8% for 500µl and 86.4% for 100µl saliva. The overall percentage of positive results in nasopharyngeal swabs and saliva specimens remained comparable throughout the study visits. We observed no significant difference in cycle number values between saliva and nasopharyngeal swab specimens, irrespective of saliva volume tested. Conclusions The saliva collection offers a promising approach for population-based testing. Implementing robust saliva-based testing strategies could contribute significantly to controlling and managing the COVID-19 pandemic.