Diagnostic performance of different pleural fluid biomarkers in tuberculous pleurisy

Due to the paucibacillary nature of tuberculous pleural effusion the diagnosis of pleural tuberculosis is challenging. This prospective study was undertaken to evaluate the diagnostic performance of ten different pleural fluid biomarkers in the differentiation between tuberculous and non-tuberculous pleural effusions. Two hundred and three patients with pleural effusion (117 men and 86 women, median age 65 years) were enrolled. Routine diagnostic work-up, including thoracentesis and pleural fluid analysis, was performed to determine the cause of pleural effusion. The following biomarkers were measured in pleural fluid: adenosine deaminase (ADA), interferon gamma (IFN-γ), interleukin 2 soluble receptor (IL-2sRα), sub-unit p40 of interleukin 12b (IL-12p40), interleukin 18 (IL-18), interleukin 23 (IL-23), IFN-γ induced protein 10 kDa (IP-10), Fas-ligand, human macrophage-derived chemokine (MDC) and tumor necrosis factor alfa (TNF-α). There were 44 (21.7%) patients with tuberculous pleural effusion, 88 (43.3%) patients with malignant pleural effusion, 35 (17.2%) with parapneumonic effusion/pleural empyema, 30 (14.8%) with pleural transudates, and 6 (3%) with miscellaneous underlying diseases. Pleural fluid IFN-γ was found the most accurate marker differentiating tuberculous from non-tuberculous pleural effusion, with sensitivity, specificity, PPV, NPV, and AUC 97%, 98%, 95.5%, 99.4%, and 0.99, respectively. Two other biomarkers (IP-10 and Fas ligand) also showed very high diagnostic accuracy with AUC≥0.95. AUC for ADA was 0.92. We conclude that IFN-γ, IP-10, and Fas-ligand in pleural fluid are highly accurate biomarkers differentiating tuberculous from non-tuberculous pleural effusion.