Diagnostic value of adenosine deaminase activity in pericardial fluids.

BACKGROUND: The activity of adenosine deaminase (ADA) was determined in serum and pericardial fluid of 70 patients (ages 21 to 71 years) with pericardial effusions of various etiologies and in 15 control subjects. METHODS: The patients were subdivided into five groups on the basis of definite diagnosis: 1) 24 patients with tuberculosis; 2) 22 with malignancies; 3) 12 with uremic pericarditis; 4) 12 with purulent pericarditis; 5) 15 control individuals without pericardial disease. The activity of ADA was determined at the same time in serum and cell-free pericardial fluid according to the method of Karker with minor modification. RESULTS: Mean (+/-SD) ADA activity in pericardial fluid was 66.92+/-4.12 IU/L in group 1; 27.50+/-6.02 in group 2; 28.65+/-4.73 in group 3; 53.05+/-11.14 in group 4; and 5.67+/-1.99 in group 5. Comparing the level achieved in group 1 with all others, the difference is significant at the p<0.001 level. When the cut-off value of 50 IU/L is used the sensitivity of the test for diagnosis of tuberculous effusion is 1, and the specificity is 0.83. Statistical analysis showed that there was no correlation between serum ADA activity and ADA activity in pericardial fluid. CONCLUSIONS: We recommend that determinations of ADA activity in pathologic pericardial fluids seem to be of great value in the early diagnosis of tuberculous pericardial effusions. Levels above 50 IU/L in effusions indicate probable tuberculosis.