The diagnostic accuracy of RT-PCR from self-collected saliva versus nasopharyngeal sampling: A systematic review and meta-analysis

OBJECTIVES: To evaluate the diagnostic utility of self-collected saliva in coronavirus desease-19 (COVID-19) screening procedures. METHODS: A total of 6 databases were reviewed from their inception until August 2021. Sensitivity and specificity were measured by extracting items (true-positive, true-negative, false-positive and false-negative) from each paper. We evaluated the diagnostic accuracy based on Quality Assessment of Diagnostic Accuracy Studies, version 2. RESULTS: A total of 41 studies were included in the final analysis. The diagnostic odds ratio (OR) of self-collected saliva was 196.2022 (95% confidence interval [CI]: 117.8833-326.5546). The area under the summary receiver operating characteristic curve was 0.955. For detecting COVID-19, self-collected saliva had a moderate sensitivity of 0.8476 [0.8045-0.8826] and positive predictive value of 0.9404 [0.9122-0.9599] but high specificity of 0.9817 [0.9707-0.9887] and negative predictive value of 0.9467 [0.9130-0.9678]. In a subgroup analysis, the diagnostic accuracy of self-collected saliva tended to be higher for symptomatic (vs. asymptomatic) examinees. CONCLUSION: Although naso/oropharyngeal swab tests are the most accurate and important diagnostic tools, the saliva-based testing method can be used as a suitable alternative test, with the advantages of increased patient convenience, efficient testing, and the need for fewer medical staff and resources. In particular, simple collecting method such as drooling or spitting without coughing would be effective in evaluating the symptomatic patients. PROSPERO no.: CRD42021279287