"LAPAGE Index In Differentiating Tuberculous Pleurisy and Malignant Pleural Effusion"

Malignant pleural effusion and tuberculous pleurisy may both present with elevated levels, making their differential diagnosis challenging. Although an ADA level ≥ 40 U/L increases the likelihood of both conditions, additional biomarkers are needed for better discrimination. Therefore, we aimed to evaluate clinical and biochemical markers that could aid in differentiating these two conditions in patients with high ADA levels.

This retrospective cohort study included patients with pleural effusion and pleural fluid ADA levels ≥ 40 U/L who were evaluated between 2014 and 2024. The cancer ratio (serum LDH/pleural ADA) and the pleural LDH/ADA ratio, previously described in the literature, were calculated. Multivariable regression analysis was performed to identify independent predictors of malignant pleural effusion.

A total of 294 patients constituted the study cohort. In multivariable regression analysis, cancer ratio was not statistically significant in differentiating malignant pleural effusion from tuberculous pleurisy. In contrast, the pleural LDH/ADA ratio, pleural protein level and age were identified as independent predictors of malignant pleural effusion. The LAPAGE index, derived from these variables [(pleural LDH / ADA) × age / pleural protein], demonstrated superior diagnostic performance in predicting malignant pleural effusion compared with individual parameters.

In patients with pleural effusion and ADA levels ≥ 40 U/L, neither the cancer ratio nor the pleural LDH/ADA ratio alone provided sufficient discriminatory power between malignant pleural effusion and tuberculous pleurisy. The LAPAGE index may serve as a useful adjunctive tool in the differential diagnosis of tuberculosis and malignancy in pleural effusions with high ADA levels.