Molecular forms of adenosine deaminase do not aid the diagnosis of tuberculosis

To investigate the diagnostic utility of adenosine deaminase as a test for tuberculosis, molecular forms of the enzyme indicative of cell-mediated immunity were studied in tuberculosis pleural effusion, peritonitis and meningitis. Twenty-six pleural, 21 peritoneal, and 24 cerebrospinal tuberculous and non-tuberculous fluids were examined for adenosine deaminase and the large and small forms of the enzyme were differentiated on immunoblots. Adenosine deaminase levels ranged from zero to 81 units/L, zero to 31 units/L and zero to 31 units/L in the pleural, peritoneal and cerebrospinal fluids, respectively. The large form of adenosine deaminase (280 kDa) was detected in one of 14 proved tuberculous cases, a peritoneal fluid. The small form of the enzyme (35-39 kDa) was seen in both tuberculous and non-tuberculous conditions in 6 pleural, 7 peritoneal and 8 cerebrospinal fluids. Molecular forms of adenosine deaminase did not appear to help in the diagnosis of tuberculosis in this patient population and may not be suited for analysis in fluids with low enzyme activity.