Comparative study of cerebrospinal fluid adenosine deaminase activity in patients with meningitis

Cerebrospinal fluid (CSF) adenosine deaminase (ADA) activity in tubercular meningitis (TBM) patients (n=20), non-tubercular meningitis (NTBM) patients (n=10) and non-tubercular non-meningitis (NTBNM) cases (n=15) were measured by the method based on Berthlot's reaction. The mean CSF ADA activity in TBM (13.62 +/- 8.45 IU/L) was found to be significantly higher as compared to NTBM (6.51 +/- 2.41 IU/ L, p<0.001) and NTBNM (2.35 +/- 1.16 IU/L, p<0.0001) respectively. The sensitivity and specificity of CSF ADA activity was 85.0% and 88.0% respectively at cut-off value of 6.97 IU/L to diagnose tubercular meningitis. The specificity and sensitivity of CSF ADA for TBM was found to be 85.0% and 70.0% as compared to NTBM and 85.0% and 100.0% as compared to NTBNM. We propose that estimation of that ADA activity in CSF of TBM patients, using a cut off value 6.97 IU/L can diagnose differentially tubercular meningitis. Since, most developing countries have the dubious distinction of having higher prevalence and incidence of tubeculosis and lack of well equipped laboratory services for proper diagnosis of tubercular meningitis, measurement of CSF ADA activity can be a better and reliable approach for the rapid diagnosis and management of tubercular meningitis vis a vis other types of meningitis.