Diagnostic value of adenosine deaminase activity in tuberculous effusions.

We read with interest the recent paper by QUEROL JM, BARBE F, MANRESA F, EsTEBAN L and CANETE [1]. The authors presented some patients with tuberculous pleural effusion and adenosine deaminase activity (ADA) values less than 43 U·I-• We reported previously that ADA values (Guisti method) were statistically significantly higher in tuberculous pleural effusions than in most other diseases [2]. High ADA values of pleural fluid (between 140 U-1·1 and 273 U-1·) were measured in five patients with rheumatoid arthritis [3]. The distinction between rheumatoid and tuberculous pleurisy must be made with other methods. A study to determine ADA in pleural fluid, bronchial washings and serum is in progress in Greece [4]. The major problem is the limit value of ADA over which tuberculosis can be diagnosed. Table 1 shows that none of our patients with tuberculous pleural effusions, confinned by bacterial cultures or pathological findings of pleural tissue, had ADA value less than 39 U·/·1• One patient with pneumonia and one patient with carcinoma had empyema with ADA pleural fluid values greater than 39 U·l·1• According to these data sensitivity and specificity, of the test in tuberculosis are at the highest point when the ADA value of pleural fluid is more than 38 U-1· or the ratio ADA pleural fluid/ADA serum is more than two (table 2). We propose diagnostic ADA values of tuberculous pleural effusions more than 38 U·J· 1 and the use of the ratio ADA pleural fluid/ ADA serum as a valuable tool to improve the accuracy of the test for diagnosis of pleural effusion.