Cerebrospinal fluid adenosine deaminase activity for the diagnosis of tuberculous meningitis in adults.

We studied adenosine deaminase (ADA) activity in cerebrospinal fluid (CSF) of 16 cases of tuberculous meningitis, 4 cases of cryptococcal meningitis, 5 cases of bacterial meningitis, 12 cases of eosinophilic meningitis, 26 cases of aseptic meningitis, 6 cases of carcinomatous meningitis and 108 cases with normal CSF. The mean CSF ADA values for the different groups were: 39.44 +/- 41.46, 13.00 +/- 7.43, 34.20 +/- 40.81, 3.17 +/- 4.82, 10.03 +/- 9.23, 8.67 +/- 13.60, and 2.58 +/- 2.90 U/I, respectively. Comparing the ADA activity between patients with tuberculous meningitis and non-tuberculous meningitis, the receiver-operating characteristic (ROC) curve identified a CSF ADA level of 15.5 U/I as the best cut-off value to differentiate between the two, with a sensitivity of 75% and a specificity of 93%, with an area under the curve of 0.92. When tuberculous meningitis was compared with aseptic and carcinomatous meningitis, the ROC curve identified a CSF ADA level of 19.0 U/I as the best cut-off value for differentiation, with a sensitivity of 69% and a specificity of 94%, with an area under the curve of 0.83. The level of CSF ADA may be useful as a complementary tool in the early diagnosis of tuberculous meningitis.