A Study on Cerebrospinalfluid Adenosine Deaminase Levels as a Marker of Central Nervous System Tuberculosis

BACKGROUND: Tuberculosis affection of the central nervous system is seen in 1 % all cases of tuberculosis. It’s a major extra-pulmonary manifestation of Tuberculosis.CNS TB is a devastating disease and the yield of AFB staining, CSF culture for MTB is low. The CSF – ADA levels have been found to be a good indirect evidence to the presence of TBM. OBJECTIVES: The study was conducted with the objective of (i) Evaluating the efficacy of CSF adenosine deaminase activity in diagnosing tuberculous meningitis. (ii) To find out a appropriate cut-off value for CSF ADA level for the diagnosis of tuberculous meningitis. METHODS: A total of 55 patients suffering from clinical features suggestive of sub-acute / chronic meningitis were included in this study and they were divided into TBM (43 patients) and non TBM group (12 patients) based on their CSF analysis , neuro – radiological imaging and response to treatment. The CSF – ADA level activity in both the groups was analysed. RESULTS: A Cut-off of 12 IU/L gives a sensitivity , specificity, positive predicitive value and a negative predictive value of 90.7 ,83.33 , 95.12 and 71.43 respectively. CONCLUSION: ADA at a cut-off of 12 IU/L can be a reliable and rapid indirect indicator of TBM