Adenosine deaminase activity in the diagnosis of lymphocytic pleural effusions of tuberculous, neoplastic and lymphomatous origin.

We studied the activity of adenosine deaminase in 74 lymphocytic pleural effusions which were divided into four groups according to the aetiology: tuberculous (38 cases), neoplastic (17), lymphomatous (7) and miscellaneous (12). The mean enzyme value was significantly higher in the tuberculous cases (93.81 +/- 29.56 U/I) than for the other three groups and significantly higher in pleural effusions of lymphomatous origin than in the neoplastic and miscellaneous groups. Based on the lowest value of enzyme activity found in the tuberculous group (50 U/I), the test had a sensitivity of 1 and a specificity of 0.97.