Head-to-head comparison of the diagnostic accuracy of pleural fluid, serum carcinoembryonic antigen, and their ratio for malignant pleural effusion: a systematic review and meta-analysis.

Background: Several studies have evaluated the diagnostic accuracy of pleural fluid and serum carcinoembryonic antigen (CEA) for malignant pleural effusion (MPE). However, it remains unclear whether the diagnostic accuracy of pleural fluid CEA is superior to that of serum CEA and pleural fluid to serum CEA ratio (CR). We performed a head-to-head systematic review and meta-analysis to assess their diagnostic accuracy. Methods: We searched the PubMed and Web of Science databases to verify studies that simultaneously investigated the diagnostic accuracy of pleural fluid, serum CEA, and CR for MPE. We assessed the quality of the included studies using the revised Quality Assessment for Diagnostic Accuracy Studies tool (QUADAS-2). A bivariate model was used to pool the sensitivities and specificities of pleural fluid, serum CEA, and CR. We used a summary receiver operating characteristic (sROC) curve to measure their global diagnostic accuracy. The Deeks test was used to estimate publication bias. Results: We included seven studies with 1,148 MPE patients and 816 benign pleural effusion (BPE) patients. The areas under the sROC curve (95% confidence interval) of pleural fluid, serum, and CR were 0.95 (0.93-0.96), 0.84 (0.81-0.87), and 0.90 (0.87-0.93), respectively. No publication bias was observed for pleural fluid CEA and CR, while serum CEA had significant publication bias. Conclusions: The diagnostic accuracy of pleural fluid CEA for MPE is superior to that of serum CEA and CR. Simultaneously testing pleural fluid and serum CEA should not be encouraged.