The role of the pleural fluid lactate dehydrogenase/adenosine deaminase ratio in differentiating between tuberculosis pleural effusion and parapneumonic effusion: a retrospective cohort study and meta-analysis

Background In regions with a high prevalence of tuberculosis, it is crucial to accurately differentiate between tuberculosis pleural effusion (TPE) and parapneumonic effusion (PPE). The current study aimed to evaluate the potential role of the pleural fluid lactate dehydrogenase (LDH)/adenosine deaminase (ADA) ratio in differentiating between TPE and PPE. Methods In the first section, the pleural fluid LDH/ADA ratio was compared between 45 patients with TPE and 81 patients with PPE within our study population, and its diagnostic efficacy was assessed. In the second section, we conducted a meta-analysis incorporating six previous publications and the current study. Results In our study population, a cut-off value of 18.63 for the pleural fluid LDH/ADA ratio was established for diagnostic performance analysis. The area under the curve (AUC) to discriminate between TPE and PPE was 0.960 [95% confidence interval (CI): 0.902 to 0.989]. As for sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), positive predictive value and negative predictive value, they were 94.44% (95% CI: 81.3% to 99.3%), 84.85% (95% CI: 73.9% to 92.5%), 6.23 (95% CI: 3.50 to 11.09), 0.065 (95% CI: 0.017 to 0.25), 77.3% (95% CI: 65.6% to 85.8%), and 96.6% (95% CI: 87.9% to 99.1%), respectively. The diagnostic accuracy of the pleural fluid LDH/ADA ratio was further tested and confirmed in the subsequent meta-analysis. The meta-analysis demonstrated that the pooled sensitivity and specificity were 90% (95% CI: 82% to 94%) and 91% (95% CI: 84% to 95%), respectively. Conclusions The current study suggests that the pleural fluid LDH/ADA ratio is a useful marker for distinguishing TPE from PPE.