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

Adenosine deaminase (ADA) activity was measured in the cerebrospinal fluid (CSF) of 27 subjects suffering from tuberculous meningitis (TBM), 19 from bacterial meningitis, 10 from encephalitis, and 10 control subjects. The mean CSF ADA level was significantly raised (P < 0.001) in TBM patients as compared to other study groups. A cut-off CSF ADA level of > 5 IU/1 was considered for the diagnosis of TBM, and the test had sensitivity and specificity of 89 and 92 per cent, respectively. Overall, it was found to be a better test in comparison to any other single test for the diagnosis of TBM. Confirmed TBM patients had significantly higher CSF ADA activity when compared with clinical TBM (P < 0.01) and the levels did not differ significantly among different stages of disease. The ADA level in TBM cases had significant correlation with CSF cell count (P < 0.01), lymphocyte percentage (P < 0.02) and protein concentration (P < 0.02). Thus, the CSF ADA activity assay was found to be a simple, useful and rapid diagnostic test for the early recognition of TBM in children.