The cancer ratio plus in the differential diagnosis of pleural effusions: a scoping review of current evidence.

Publication date: Feb 15, 2026

Differentiating between malignant pleural effusion (MPE) and tuberculous pleural effusion (TPE) remains challenging in clinical practice. The cancer ratio plus (CR+), a potential diagnostic tool calculated as serum lactate dehydrogenase/(pleural adenosine deaminase x pleural lymphocyte percentage) has emerged to address this diagnostic challenge. This scoping review maps the available evidence on its diagnostic performance. We conducted a systematic search of PubMed, Scopus, and Web of Science databases from inception to April 2025. Eligible studies assessed the accuracy of CR+ in distinguishing MPE from TPE. Data on study design, cut-off values, sensitivity, specificity, area under the curve (AUC), and likelihood ratios were extracted and synthesized narratively. Six studies comprising 881 patients were included. Reported cut-off values varied widely (5. 7 – 41. 0), as did sensitivity (74. 3 – 97. 6%) and specificity (36. 6 – 94. 1%). Most studies, however, reported good discriminatory power with AUC values generally above 0. 80. The highest diagnostic accuracy was observed in one study, which reported a sensitivity of 97. 6%, a specificity of 94. 1%, and an AUC of 0. 86. Differences in cut-off thresholds, study populations, local tuberculosis epidemiology, and laboratory methodology (particularly lymphocyte quantification) likely contributed to this heterogeneity. The CR+ appears promising as a non-invasive tool using routine parameters for differentiating MPE from TPE, but diagnostic performance varies across settings. The heterogeneity in optimal cut-off values highlights the need for local validation before clinical adoption. Future research should standardize methodology and assess its impact on decision-making and patient outcomes.

Semantics

Original Article