Utility of Cancer Ratio (Serum LDH/Pleural Fluid ADA) and Cancer Plus Ratio (Cancer Ratio/Pleural Fluid Lymphocytic Percentage) in Differentiating Malignant Pleural Effusion and Tubercular Pleural Effusion: A Prospective Observational Study

Background Tubercular and malignant pleural effusions are two common causes of exudative effusions in high TB burden countries. Differentiating them accurately is crucial for timely management. Traditional biomarkers often overlap, prompting the need for more specific diagnostic tools. The Cancer Ratio (serum LDH/pleural fluid ADA) and Cancer Plus Ratio (Cancer Ratio/pleural fluid lymphocyte %) offer promising potential in differentiating tubercular and malignant pleural effusion. Methods This prospective observational study included 179 patients with lymphocytic exudative pleural effusion. Serum LDH, pleural ADA, and lymphocyte % were measured. Cancer Ratio and Cancer Plus Ratio were computed. Diagnosis was confirmed via cytology, GeneXpert, or pleural biopsy and, in cases of clinically diagnosed tubercular pleural effusion, by clinical and radiological improvement. Diagnostic efficacy was assessed using sensitivity, specificity, and ROC analysis. Results Cancer Ratio and Cancer Plus Ratio were significantly higher in malignant pleural effusion (MPE) than in tubercular pleural effusion (TPE). Cancer Plus Ratio had the best diagnostic performance with a sensitivity of 95.1% and specificity of 93.3%. Conclusions Cancer Ratio and Cancer Plus Ratio are effective, low-cost, non-invasive tools to differentiate MPE from TPE, with Cancer Plus Ratio demonstrating the highest diagnostic value. Trial Registration: CTRI/2024/04/065096 (Registered on 02/04/2024)