Can blood and salivary biomarkers replace biopsy as a diagnostic tool?

Data sources The online databases of Medline, Web of Science, Embase and Cochrane Library were systematically searched to identify articles published (up to October 2021) on the accuracy of microRNAs (miRNAs) in the diagnosis of oral squamous cell carcinoma (OSCC).Study selection Primary research studies involving human participants with the presence of healthy controls and sufficient data for statistical analysis were included. Exclusion criteria included review articles, letters, case reports and non-human trials. Two reviewers independently assessed the studies, and any conflicts were resolved by consulting a third reviewer. From 326 initially identified articles, 20 articles (all case-control studies) were included in the meta-analysis involving 1,106 cases and 732 controls.Data extraction and synthesis Data extracted included sensitivity, specificity, likelihood ratios and diagnostic odds ratios for blood and salivary miRNAs. A combined category of body fluid miRNAs was also synthesised. Heterogeneity between studies was evaluated using Cochran's Q test and I2 statistic. Quality assessment of the studies was performed using the Quality Assessment of Diagnostic Accuracy Studies criteria (QUADAS-2). Meta-analysis was performed based on a random-effects model. A comparison of the diagnostic accuracies between blood and salivary miRNAs was carried out using the summary receiver operator characteristic curve (SUROC) including the area under the curve (AUC). P <0.05 was considered as statistically significant.Results Risk of bias was deemed to be moderate; however, patient selection bias was high due to 15 studies lacking randomisation. Heterogeneity between studies was high. Meta-analysis revealed that for body fluid miRNAs, sensitivity was 0.78 (95% CI: 0.73-0.83), specificity was 0.82 (95% CI: 0.77-0.86), AUC value was 0.87 (95% CI: 0.84-0.90), and positive and negative likelihood ratios were 4.3 (95% CI: 3.4-5.4) and 0.27 (95% CI: 0.22-0.34), respectively. The diagnostic odds ratio was 16 (95% CI: 11-23).Conclusions Body fluid miRNAs may provide moderate accuracy in diagnosing OSCC; however, the significant heterogeneity between studies and the lack of large-scale high-quality studies limits their diagnostic value.