Pleural fluid adenosine deaminase and interferon gamma as diagnostic tools in tuberculosis pleurisy.

Several biological markers have been proposed to improve the efficacy of diagnosing tuberculous pleurisy. The study was undertaken to evaluate the accuracy of pleural fluid adenosine deaminase (ADA) activity and interferon-gamma (IFN-gamma) concentration in differentiating tuberculous pleural effusion (TPE) and nontuberculous pleural effusion (non-TPE). Ninety four patients (50 M and 44 F, mean age 60+/-18, range 18-95 years) with pleural effusion (PE) were studied. TPE was diagnosed in patients with: (i) positive pleural fluid or pleural biopsy culture or (ii) granulomas in the pleural biopsy specimen, after exclusion of other granulomatous diseases. Pleural fluid ADA activity was measured with the colorimetric method of Giusti, while IFN-gamma level was measured with ELISA. TPE was diagnosed in 28 patients. The non-TPE group consisted of 35 patients with malignant PE, 20 patients with parapneumonic effusion/pleural empyema, 5 with pleural transudate, and 6 with miscellaneous PE. The ADA activity and IFN-gamma concentration were significantly higher in TPE than in non-TPE (614.1+/-324.5 vs. 15.1+/-36.0 pg/ml, P<0.0001 and 75.1+/-39.1 vs. 11.0+/-16.6 U/l respectively, P<0.0001). The diagnostic sensitivity and specificity of IFN-gamma measurement (cut-off value of 75.0 pg/ml) were 100% and 98.5% respectively and were similar to those of ADA (100% and 93.9% at the cut-off value of 40.3 U/L). We conclude that pleural fluid ADA activity and IFN-gamma concentration are highly sensitive and specific markers of tuberculous pleurisy.