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 GeneFiX™ 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 RT-PCR 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 GeneFiX™ 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