Evaluation of the efficacy of tongue swab and saliva as samples for testing COVID-19 infection in symptomatic cases in comparison with nasopharyngeal swab

Introduction. COVID-19 caused by SARS CoV-2 continues to be a major health concern globally. Methods for detection of the disease are necessary for public health efforts to monitor the spread of this disease as well as for detecting the emergence of new variants. Gap statement. Collection of Nasopharyngeal swab (NPS), the gold standard sample for the detection of COVID-19 infection by RT-qPCR is invasive and requires the expertise of a trained medical provider. This highlights the need for validating less invasive samples that can be self-collected without the need for trained medical provider. Aim. To validate saliva and tongue swab as potential samples for the diagnosis of COVID-19. Methodology. Adult and paediatric cases who had acute influenza like illness were enrolled in the study. The study involved comparison of Nucleic Acid Amplification Tests (NAAT) results for the detection of COVID-19 obtained by using saliva and tongue swab with that of NPS. Result and Conclusion. The sensitivity and specificity of saliva as sample for COVID-19 detection were found to be 71 and 88% respectively whereas those of tongue swab as sample were 78 and 90%. Further validation was based on the positive and negative predictive values, the likelihood ratio, agreement percentage and the kappa statistic. The findings of the study point towards tongue swab and saliva as suitable alternative samples for the diagnosis of COVID-19 with a slightly higher accuracy and agreement for tongue swab than saliva. However considering the fatality of COVID-19, they are better suited for mass screening of people than for diagnosis.