Adenosine deaminase estimations in the differentiation of pleural effusions

Adenosine deaminase (ADA) estimations were performed on the pleural fluid from 368 effusions. The mean (+/-SD) ADA concentration in tuberculous effusions was 92,11 +/- 37,05 U/l, and these values were found to be highly statistically different from the 23,23 +/- 13,15 U/l in secondary malignant tumours of the pleura, the 34,86 +/- 14,2 U/l in mesotheliomas, and the 23,81 +/- 15,07 U/l in pulmonary embolism. The ADA values of 64,3 +/- 44,95 U/l in lymphoproliferative disorders were less significantly different. No statistical difference could be found between values in the tuberculous group and the ADA levels of 97,57 +/- 82 U/l found in para-infective effusions, but these could be distinguished from each other by microscopic examination of the pleural fluid. The importance of ADA estimations in the diagnosis and differentiation of tuberculous effusions is discussed and the role of microscopy is emphasized.