Background: Tuberculous pleural effusion (TPE) and parapneumonic effusion (PPE) areoften difficult to differentiate owing to the overlapping clinical features. Observationalstudies demonstrate that the ratio of lactate dehydrogenase to adenosine deaminase(LDH/ADA) is lower in TPE compared to PPE, but integrated analysis is warranted. Methods: We conducted a systematic review to evaluate the diagnostic accuracy of theLDH/ADA ratio in differentiating TPE and PPE. We explored the PubMed and Scopusdatabases for studies evaluating the LDH/ADA ratio in differentiating TPE and PPE. Results: From a yield of 110 studies, five were included for systematic review. The cutoffvalue for the LDH/ADA ratio in TPE ranged from <14.2 to <25. The studies demonstratedhigh heterogeneity, precluding meta-analysis. Quality Assessment of DiagnosticAccuracy Studies Tool 2 assessment revealed a high risk of bias in terms of patientselection and index test. Conclusion: LDH/ADA ratio is a potentially useful parameter to differentiate betweenTPE and PPE. Based on the limited data, we recommend an LDH/ADA ratio cutoff valueof <15 in differentiating TPE and PPE. However, more rigorous studies are needed tofurther validate this recommendation.