ADA and meningeal tuberculosis: Results of our study indicate that ADA level estimation in CSF is not only of considerable value in the diagnosis of TBM, CSF ADA level 10 U/L as a cutoff value exhibited 94.73% sensitivity and 90.47% specificity in differentiating tuberculous from non-tuberculous meningitis; it also has 90.00% positive predictive value and 95.00% negative predictive value.