ADA and empyema: It is worth to note that the isolated positivity of ADA(25.8 IU/L) have resulted in a mistaken diagnosis of 7/46 (15,2%) cases in non-PlTB group (2 systemic erythematous lupus, 2 lymphomas, 1 poorly differentiated cancer, 1 empyema, 1 undefined diagnosis) if only this diagnostic test was used.