The diagnostic value of pleural fluid biomarkers in tuberculous pleurisy (TP) is firmly established. However, it is less clear whether patients' age affects the diagnostic accuracy of TP biomarkers. The aim of the study was to assess the impact of age, on the predictive value of ADA, IFN-γ, IP-10 and Fas ligand in patients with pleural effusion.

The study included 222 patients, median age 64.5 (54–77) years, 58.6% men, with pleural effusion: TPE (60 patients; 27.0%), malignant PE (90 patients; 40.5%), parapneumonic effusion/pleural empyema (35 patients; 15.8%), pleural transudate (30 patients, 13.5%) and other causes of PE (7 patients; 3.2%). The odds ratio for the diagnosis of TPE significantly decreased with increasing age (OR = 0.62/10 years) and significantly increased with increasing level of all evaluated pleural fluid biomarkers. Age affected the diagnostic accuracy of ADA with a trend towards reduction in OR for TPE in older patients (P = 0.077, 95% CI 0.59–1.03).

Younger age and high pleural fluid ADA level are associated with very high probability of TP. This probability significantly decreases not only with decreasing pleural fluid ADA, but also with increasing age. Patient's age does not affect the diagnostic yield of pleural fluid IFN-γ, IP-10 and sFas.