Value of adenosine deaminase level for the differential diagnosis various meningitis

Objective :- Tuberculosis kills 3.70 lakh patients in India every year, out of which 7-12 % are with meningeal involvement. Delay in its diagnosis and initiation of treatment results in poor prognosis and squeal in up to 25% of cases. The aim of the present study is to look for a simple, rapid, cost effective and fairly specific test in differentiating tubercular etiology from other causes of meningitis. In the present study we measured the adenosine deaminase (ADA) activity in cerebrospinal fluid (CSF) of TBM and non-TBM patients. Material and method : 150 patients were studied and divided into four groups: TBM culture positive, TBM culture negative pyogenic meningitis and viral meningitis, depending upon the accepted criteria. CSF was drawn and ADA Value estimated. Results : Out of 65 tubercular patients, 64 had CSF ADA at or above the cutoff value while one had below. Out of 85 non- tuberculous patients, two had ADA levels at or above the cutoff value while 83 had below this value, Cut off value of test was 9 IU. For diagnosis of Tuberculous Meningitis specificity of the test is 97.65 Sensitivity is 98.46; positive predictive value is 98.81 with negative predictive value of 96.97. Conclusion :- It can be concluded that ADA estimation in CSF is not only simple, inexpensive and rapid but also fairly specific method for making a diagnosis of tuberculous etiology in TBM, especially when there is a dilemma of differentiating the tuberculous etiology from non-tuberculous ones. For this reason ADA estimation in TBM may find a place as a routine investigation.