Diagnostic accuracy of fresh drooled saliva for SARS-CoV-2 in travelers

Background: The standard for SARS-CoV-2 diagnosis is RT-PCR from nasopharyngeal or oropharyngeal swabs. Major airports require COVID-19 screening, and saliva has the potential as a substitute specimen for SARS-CoV-2 diagnosis. We investigated the utility of fresh drooled saliva against NPS for COVID-19 screening of travelers. Methods: We recruited 81 travelers and 15 non-travelers (including ten controls) prospectively within a mean of 3.22 days of RT-PCR confirmed COVID-19. Each study participant provided 2 mls of early morning fresh drooled whole saliva separately into a sterile plastic container and GeneFiXTM saliva collection kit. The saliva specimens were processed within 4 h and tested for SARS-CoV-2 genes (E, RdRP, and N2) and the results compared to paired NPS RT-PCR for diagnostic accuracy. Results: Majority of travellers were asymptomatic (75.0%) with a mean age of 34.26 years. 77 travelers were RTPCR positive at the time of hospitalization whilst three travelers had positive contacts. In this group, the detection rate for SARS-CoV-2 with NPS, whole saliva, and GeneFiXTM were comparable (89.3%, 50/56; 87.8%, 43/49; 89.6%, 43/48). Both saliva collection methods were in good agreement (Kappa = 0.69). There was no statistical difference between the detection rates of saliva and NPS (p > 0.05). Detection was highest for the N2 gene whilst the E gene provided the highest viral load (mean = 27.96 to 30.10, SD = 3.14 to 3.85). Saliva specimens have high sensitivity (80.4%) and specificity (90.0%) with a high positive predictive value of 91.8% for SARS-CoV-2 diagnosis. Conclusion: Saliva for SARS-CoV-2 screening is a simple accurate technique comparable with NPS RT-PCR.