Pleural fluid interferon-gamma and adenosine deaminase levels in tuberculosis pleural effusion: a cost-effectiveness analysis.

Pleural fluid levels of interferon-gamma (IFN-gamma) and adenosine deaminase (ADA) have been found to be high in patients with tuberculosis (TB). The present study was carried out to compare the diagnostic utility of these two markers and to carry out a cost-effectiveness analysis of performing IFN-gamma estimation in comparison to ADA. A total of 52 patients with pleural effusion, 35 of which were found to have TB etiology, were prospectively included for estimation of ADA and IFN-gamma levels. The difference in the cost of performing the two diagnostic tests was compared with the cost of the treatment for a patient with TB. Pleural fluid IFN-gamma (median [range]: 2,100 [70-14,000] vs. 3 [0-160]; P<0.001) as well as ADA levels (mean [SD]: 93.1 [62.3] vs 15.4 [8.7]; P<0.001) were significantly higher in patients with TB effusion. Even though IFN-gamma estimation was more sensitive (97.1 vs. 91.4%), the extra cost of IFN-gamma estimation for detecting one patient with TB was found to be equivalent to the cost of a complete course of antituberculosis treatment for six patients. In developing countries, where TB is rampant and cost is a major concern, pleural fluid IFN-gamma estimation does not seem to be a cost-effective investigation method for differentiating TB from non-TB pleural effusion.