Utility of cell-free DNA in diagnosing tuberculous pleurisy: A systematic review and meta-analysis protocol

Background: Tuberculous pleurisy is the most common form of extrapulmonary tuberculosis. Diagnosis remains challenging due to the paucibacillary nature of pleural effusions, leading to low sensitivity of conventional microbiological methods and frequent reliance on invasive biopsy. Cell-free DNA (cfDNA), comprising fragmented genetic material released from host cells and pathogens into biofluids, presents a promising minimally-invasive biomarker. This protocol outlines a systematic review and meta-analysis designed to evaluate the overall diagnostic accuracy of cfDNA for tuberculous pleurisy and to identify factors influencing its performance. Methods: This protocol is prospectively registered with PROSPERO. We will systematically search PubMed, Embase, Web of Science, Scopus, The Cochrane Library from inception to June 2027. Diagnostic accuracy studies directly comparing cfDNA detection (in pleural fluid, plasma/serum) against a composite reference standard for tuberculous pleurisy (including microbiological, histological, or clinical diagnosis) will be included. Two reviewers will independently screen studies, extract data, and assess risk of bias using the QUADAS-2 tool. A bivariate random-effects meta-analysis will be performed to calculate pooled sensitivity, specificity, positive/negative likelihood ratios, and diagnostic odds ratios. A hierarchical summary receiver operating characteristic curve will be plotted. Subgroup analyses and meta-regression will explore sources of heterogeneity. The GRADE approach will be used to evaluate the certainty of evidence. Conclusion: This review will provide pooled estimates of the diagnostic sensitivity and specificity of cfDNA for tuberculous pleurisy, evaluate its clinical utility, and identify key factors—such as sample type, detection technology, and pre-analytical procedures—associated with optimal performance. The findings will offer high-level evidence to guide clinical application and future research.