Self-collected saliva: Diagnostic potential for severe acute respiratory syndrome coronavirus-2 testing in a resource-limited setting

Abstract

Background: The gold standard for the diagnosis of coronavirus (CoV) disease 2019 in the hospital and community setting is by the real-time reverse transcription-based polymerase chain reaction (RT-PCR) using the respiratory samples. The collection of nasopharyngeal or oropharyngeal swab (NP/OP) needs experienced medical personal and appropriate biosafety conditions. There is need for a simpler strategy for the sample collection without compromising the sensitivity. Saliva sample collection is noninvasive. Therefore, the primary objective of the study was to evaluate the efficacy of severe acute respiratory syndrome CoV-2 (SARS-CoV-2) RT-PCR using self-collected saliva specimen. Materials and Methods: This pilot study was carried out at an Indian Council of Medical Research (ICMR) approved molecular laboratory. Self-collected saliva and OP/NP swab in the viral-transported medium (VTM) were collected in parallel from the study participants and processed for SARS-CoV-2 RT-PCR. Cycle threshold (Ct) value of envelope gene (“E”), HKU Orf 1b gene (“HKU”), and Actin (internal control) obtained for saliva and NP/OP swab were tabulated. Results: Saliva and OP/NP swab in parallel were collected from 85 individuals. The mean age of the study population was 35.2 years, and 81% were male. The overall sensitivity and specificity of RT PCR on the saliva sample were 95.6% and 92.5%. The concordance between 'E” and “HKU” Ct value obtained by NP/OP and saliva RT-PCR was 97.64% and 95.29%. The positive and negative predictive value of the novel method was 93.5% and 94.9%, respectively. Conclusion: Self-collected saliva is a reliable biological sample and promising tool for SARS-CoV-2 testing in the resource-limited setting.