Cerebrospinal fluid C reactive protein and adenosine deaminase in meningitis in adults

To assess the utility of C-reactive protein (CRP) levels and adenosine deaminase (ADA) activity in the cerebrospinal fluid (CSF) as rapid screening tests to differentiate various types of meningitis in adults and to establish a cut off level for ADA.

CSF samples were obtained from 50 patients who presented to the emergency room and out-patient of Sri Siddhartha Medical Hospital, Tumkur during the period between August 2006 and September 2008. Diagnosis of meningitis was based on the clinical presentation and CSF analysis.

Out of a total of 50 patients who were enrolled in the study, 24 were diagnosed as tubercular meningitis (TBM) based on the clinical features and CSF analysis. The mean Adenosine deaminase (ADA) activity was 14.14 +/- 7.44 U/l in the TBM group. The sensitivity and specificity was 73.9% and 92.6% respectively when a cut-off value of ADA of 10U/l was used, with an accuracy of 84%. CSF-C Reactive protein (CRP) was significantly higher in pyogenic meningitis compared to non-pyogenic meningitis. The sensitivity and specificity of the test was 83.3% and 100% respectively with an accuracy of 98%.

2 rapid screening tests- CRP and ADA activity in the CSF can help in the differential diagnosis of pyogenic from non-pyogenic meningitis and tubercular from viral meningitis respectively. CRP being elevated in pyogenic meningitis and ADA activity noted to be higher in TBM. The levels of ADA and CRP were found to be low in viral meningitis.