Development of a diagnostic nomogram for tuberculous pleural effusion.

Background: Tuberculous pleural effusion (TPE) is a common form of extrapulmonary tuberculosis and remains difficult to diagnose, particularly when distinguishing it from malignant and parapneumonic pleural effusions. Although pleural fluid adenosine deaminase (ADA) is widely used, its diagnostic accuracy varies across clinical settings and may be affected by other exudative pleural diseases. This study aimed to develop and validate a diagnostic nomogram based on readily available biomarkers to improve the accuracy of TPE diagnosis. Methods: We performed a case-control study in patients with exudative pleural effusion. Clinical characteristics and serum and pleural fluid biomarkers were analyzed. Independent predictors identified by logistic regression were incorporated into a diagnostic nomogram. Model performance was assessed using receiver operating characteristic (ROC) curve analysis, calibration plots, and decision curve analysis (DCA). Results: Seventy-nine patients were included, comprising 39 with confirmed TPE and 40 with non-TPE effusions (33 malignant and 7 parapneumonic). Pleural fluid ADA ≥ 40 U/L, serum ADA ≥ 29.2 U/L, and pleural fluid protein ≥ 46.5 g/L were independent predictors of TPE. The nomogram achieved an area under the ROC curve of 0.98 (95% CI: 0.95-1.00), with 97% sensitivity, 91% specificity, and 94% overall accuracy. Calibration showed excellent agreement between predicted and observed probabilities, and DCA demonstrated superior net clinical benefit over treat-all or treat-none strategies. Conclusions: This nomogram, based on routine laboratory biomarkers, provides a highly accurate and cost-effective tool for diagnosing TPE, particularly in resource-limited, high-burden settings. External validation in larger and more diverse populations is still required.