Diagnostic value of cerebrospinal fluid adenosine deaminase determination

We measured the activity of adenosine deaminase (ADA) in the cerebrospinal fluid of 3 patients with tuberculous meningitis, 38 with viral meningitis, 15 with bacterial meningitis, 5 with malignant lymphoma, 11 with cerebrovascular diseases and 13 with miscellaneous neurological disorders. The highest ADA activities were observed in patients with tuberculous meningitis (median 21.3 U/l, range 20.0-23.0) and lymphoma (13.0 U/l, range 4.0-25.0). The sensitivity of the test for diagnosing tuberculous meningitis was 100% and the specificity 99% when a cut-off value of 20.0 U/l was used. We conclude that determination of ADA in cerebrospinal fluid is useful for the diagnosis of tuberculous meningitis, but that high activity also can be seen in some other CNS disorders, e.g. lymphoma with meningeal involvement.