ADA and tuberculosis: Acid fast stain of pleural biopsy was positive in 16 cases (22%), which correlates well with the study of Valdes L et al. (25.8%).[15] It appears that pleural fluid ADA level above 70 U/L is highly suggestive of tuberculous pleuritis where as pleural fluid ADA level below 40 U/L virtually rules out the diagnosis of tuberculosis.[1] This finding correlates well with our finding where thirteen patients had ADA level > 70 U/L and among them eleven were histopathologically proved tuberculosis; in nine histopathologically proved tuberculosis cases ADA levels were in the range 40-69 U/L.