M-02: Study of Cerebrospinal Fluid Adenosine Deaminase for Differential Diagnosis of Tuberculous and Non-tuberculous Meningitis
Seema Subedar Singh
Sasoon Hospital India
To look for a simple, rapid, cost effective, and a specific test in differentiating tubercular etiology of meningitis from other causes of meningitis by measuring the adenosine deaminase activity (ADA) in Cerebrospinal Fluid (CSF).
Total 80 patients admitted in hospital with signs and symptoms of meningitis were selected and divided into two groups: Group 1(Cases): 40 patients of tuberculous meningitis, GROUP 2(control): 40 patients of pyogenic and viral meningitis. CSF was drawn and ADA estimated.
All the calculations were done using Microsoft Excel 2010 and statistical analysis was done using SPSS statistics version 16 .The collected data was analyzed by applying student’s unpaired ‘t’ test. Total 101 patients were selected for the study, out of which forty patients (50 %) having fulfilled the criteria were labeled as tubercular, while the other 40 (50%) were labeled as non-tubercular. These 40 patients were further classified to bacterial meningitis (25) and viral meningitis (15) .Remaining patients were taken as non-conclusive.
In the present study, the mean age of TBM and non-TBM was 50.25 and 46.7 years respectively. The male female ratio was 1.35 and 2.63 in TBM and non-TBM respectively. As per the age distribution, TBM was found to be more common with more than 60 years age group where as in non-TBM patients no such association was seen with any particular age group.
Among these 40 tuberculous meningitis patients, 38 had ADA level above cut-off value and 2 had ADA below cut-off .Out of 40 patients classified as non-tubercular, 37 had ADA below cut-off and 3 had above the cut-off. Cut- off has been taken as 6IU/L and was determined based on Receiver Operating Curve.
In tuberculous group ADA activity in CSF ranged between 1.1 to 37.1I U/L with a median of 10.87and mean SD as 7.72 (ADA = 6) which was significantly higher than non-tuberculous group ADA activity which ranged between 0 to 5.1 U/L with a median of 2.44, mean SD as 1.757(ADA <6). With a cut-off of 6IU/sensitivity of ADA was found to be 95 percent and specificity is 92.5 percent .The positive predictive value is 92.68 and negative predictive value is 94.8. On comparison of the values of CSF ADA in the two groups, t cal is -6.75 and the difference in these two values was found to be highly significant (p<0.01).
Based upon the findings of this study, we found the sensitivity of the test to be 95%; specificity 92.5%, positive predictive value is 92.68 % and negative predictive value 94.8%, and so 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. For this reason CSF ADA estimation in TBM may find a place as a routine investigation. As a screening test, the determination of ADA activity in CSF can help the physician detect TBM early and reduce irreversible brain damage and neurologic sequelae by early administration of anti-tuberculous medications. But considering high ADA activity in some patients with non-TB M, CSF ADA activity should only be used in addition to evaluations of the patient’s condition and clinical symptoms.