Raised adenosine deaminase in the cerebrospinal fluid: A tool for the diagnosis of tuberculous meningitis in developing countries.

CONTEXT: The rapid diagnosis followed by the early treatment of tuberculous meningitis (TBM) is important in preventing fatal outcomes. The mainstay of diagnosis lies in cerebrospinal fluid (CSF) analysis, radiological investigations, and clinical findings.

AIM: The present study was conducted to determine the efficacy, sensitivity, and specificity of raised adenosine deaminase (ADA) level in CSF to differentiate TBM from non-TBM cases as a rapid, cost-effective, and noninvasive test.

PATIENTS AND METHODS: This was a retrospective study conducted over a 1-year period in a tertiary teaching institute of Malwa region, India. A total of 143 patients presented with symptoms and signs of meningitis were included and divided into TBM and non-TBM groups on the basis of the diagnostic criteria. CSF ADA estimation was drafted and analyzed by using ≥10 U/L as a cutoff value. A statistical comparison of the ADA levels between the study groups was made by using unpaired Student's t-test.

RESULTS: Out of the 143 cases, 40 were TBM, and 103 were non-TBM. The mean ADA level in TBM and non-TBM cases was 17.18 ± 9.59 and 6.33 ± 2.48, respectively, and the difference was statistically significant. Using a cutoff level ≥10 U/L, CSF ADA had a sensitivity of 92.5% and a specificity of 89.32%. Positive and negative likelihood ratios of the test were 8.66 and 0.08, respectively, and positive and negative predictive values, were 77.08 and 96.84%, respectively.

CONCLUSION: The present study reflects the importance of a CSF ADA level ≥10 U/L in the diagnosis of TBM. Thus, it can be used as an adjunctive diagnostic tool to differentiate TBM from other non-TBM cases, when there is a diagnostic dilemma.