Comparison of cerebrospinal fluid adenosine deaminase concentration of tuberculous and non-tuberculous meningitis

Diagnosis of tuberculous meningitis is difficult because of its non-specific clinical presentations which may be confused with other disorders of central nervous system. The initiation of anti-TB medication can often be delayed because of lack of available laboratory tests. This study was aimed at evaluating the adenosine deaminase (ADA) concentration in differentiating tuberculous meningitis from non-tuberculous meningitis to determine the cut-off point of ADA in the cerebrospinal fluid (CSF) of tuberculous meningitis patients. In this descriptive-analytical study, 42 meningitic patients (21 patients with tuberculous meningitis and 21 with non-tuberculous meningitis) admitted to Boali, Khatam al anbia and Ali ebne Abitaleb hospitals in Zahedan between 2006 and 2007 were selected. From each patient 5 ml of CSF was taken and sent to laboratory to analyze ADA concentration, cells, blood sugar, protein, smear and culturing of Mycobacterium tuberculosis. ADA concentration of CSF in TB meningitic patients was compared with that of non-TB meningitis patients. By using receiver operator characteristics curve (ROC), the optimal Cut-off point for tuberculous meningitis was determined. Out of 21 patients with TB meningitis, 17 (81%) were males and 4 (19%) females; and out of 21 patients with non-TB meningitis 14 (66%) were males and 7 (34%) were females. There was a statistically significant difference (P<0.0001) between mean of ADA levels in CSF among the TB and non-TB meningitic patients. The cut off value for the diagnosing of TB meningitis was 10.5 U/L with a sensitivity of 80.95% and specificity of 85.71%. This study demonstrated that ADA concentration in the CSF of TB meningitis patients, using a cut off value 10.5 U/L, can be useful in diagnosing of TB meningitis in Sistan and Balochestan province.