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

ObjectiveTo evaluate the usefulness of serum and CSF adenosine deaminase (ADA) activity for the diagnosis of tuberculous meningitis (TBM) from other meningitis.MethodsWe studied CSF and serum ADA activity for 83 cases of TBM, 148 of bacterial meningitis (BM), and 262 of viral or aseptic meningitis.ResultsThe 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.ConclusionsThe determination of CSF and serum ADA activity is a simple and reliable test for differentiating TBM from other types of meningitis.