[Adenosine deaminase activity in the pleural effusion. A study of 64 cases]

Clinical and analytic data of 64 patients with firm etiologic diagnosis of pleural effusion with adenosine deaminase (ADA) present, were analyzed retrospectively. The patients had entered our hospital over a 40-month period. ADA activity in pleural fluid was analyzed by the Blake and Berman kinetic method. Mean ADA activity of the total sample was 32 U/l (SD:23.9). In patients with tuberculous pleural effusion ADA activity was higher than in the remaining patients (47.7, SD:21.4, versus 15.5 SD: 13.2; p < 0.0001). In the group of patients with tuberculous pleuritis diagnosed by pleural biopsy (22 cases) the presence of necrotizing granulomas was associated with slightly higher ADA activity although the difference was not statistically significant (49.2 SD 10.1 versus 41.3 SD 8.9; p = 0.07). Among only patients with tuberculous pleuritis or neoplasia with lymphocytic exudate, a cut off point greater than 23 U for ADA predicted a diagnosis of tuberculous pleuritis with a sensitivity of 0.96, specificity of 1, positive predictive value of 1, negative predictive value of 0.94, and a confidence limit of 0.97. In conclusion, ADA activity greater than 23 U determined by the kinetic method in pleural fluid with signs of lymphocytic exudate is strongly suggestive of pleural tuberculosis based on our sample of patients with pleural effusion.