Cytokines in pleural liquid for diagnosis of tuberculous pleurisy

An elevated level of adenosine deaminase (ADA) in pleural liquid has been considered as a supplemental diagnostic marker for tuberculous pleurisy. However, this is complicated by false-positives and -negatives. Recently, it has been revealed that various cytokines are intimately involved in the pathognomonic physiology of tuberculosis. In this study, interleukin-8 (IL-8), tumour necrosis factor alpha (TNF alpha) and interferon gamma (IFN gamma) were compared with ADA in pleural liquid of patients with inflammatory (21 cases), malignant (28 cases) and tuberculous (21 cases) disease. The pleural ADA, IL-8, TNF alpha and IFN gamma levels in the tuberculous group were higher than in the other three groups. Analysis of receiver operating characteristic (ROC) curves, to evaluate the utility of the various parameters, demonstrates values for the area under the curve (AUC) of 0.770, 0.875. 0.892 and 0.987, respectively for IL-8, TNF alpha, ADA and IFN gamma,. No false-positives were encountered with IFN gamma and only one case with a small volume of pleural liquid was a false-negative. This indicates that IFN gamma is a very reliable marker of tuberculous pleurisy.