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

Mohd Thabit, Alif Adlan; Peariasamy, Kalaiarasu M.; Kuan, Pei Xuan; Fern Ying, Denisa Khoo; Nheu, Nelson; Cyncynatus, Camille; Mu'iz Arifin, Muhamad Afiq; Shamsuddin, Amira Naziffa; Yamin, Mohd Asri; Mohd Padzil, Muhammad Ashraf; Rajasekaram, Ganeswrie; Giddy, Martin; Sivaneson, Sivasooriar; Lakhbeer Singh, Harvinder Kaur; Azman, Adleen; Hassan, Afifah Haji; Chidambaram, Suresh Kumar

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.