Adenosine deaminase activity in cerebrospinal fluid and serum for the diagnosis of tuberculous meningitis.

OBJECTIVE: To evaluate the usefulness of serum and CSF adenosine deaminase (ADA) activity for the diagnosis of tuberculous meningitis (TBM) from other meningitis.

METHODS: We studied CSF and serum ADA activity for 83 cases of TBM, 148 of bacterial meningitis (BM), and 262 of viral or aseptic meningitis.

RESULTS: The mean ADA activities (IU/L) in CSF and serum were higher in TBM (11.80 ± 2.50, 30.28 ± 7.30) than in other types of meningitis (8.52 ± 3.60, 17.90 ± 9.20 in BM; 5.26 ± 1.90, 8.56 ± 5.9 in viral or aseptic meningitis). When we accepted a serum ADA activity cut-off value of 15 IU/L for the differential diagnosis of TBM and non-TBM with ROC analysis, the sensitivity was 84% and specificity was 82%. Combining CSF (≥ 10) and serum (≥ 15) ADA activity significantly increased overall specificity from 92% to 97% for the diagnosis of TBM.

CONCLUSIONS: The determination of CSF and serum ADA activity is a simple and reliable test for differentiating TBM from other types of meningitis.