title: Diagnostic efficacy of adenosine deaminase levels in cerebrospinal fluid in patients of tubercular meningitis: A comparison with PCR for Mycobacterium Tuberculosis.
abstract: BACKGROUND
  The rapid diagnosis of Tubercular meningitis (TBM) is fundamental to clinical outcome. The key to diagnosis lies in Cerebrospinal fluid (CSF) analysis and radiological investigations. There are numerous lacunae in the confirmation of diagnosis of TBM from CSF.
  
  
  OBJECTIVE
  The aim of present study was to compare the efficacy of CSF adenosine deaminase (ADA) level assays and Polymerase chain reaction (PCR) for Mycobacterium tuberculosis (M. tuberculosis) in the diagnosis of TBM.
  
  
  METHODS
  Fifty four adult patients with suspected TBM and 37 controls were included in the study and CSF analyzed for ADA and PCR for M. tuberculosis. The cases were subdivided into definite (5), highly probable (22), probable (22) and possible TBM (5) as per previously validated criteria. The first two were grouped as "most likely" TBM (27) and last two as "unconfirmed" TBM (27).
  
  
  RESULTS
  The mean ADA of the "most likely" TBM was 29±24, "unconfirmed" TBM was 21 ± 15 and controls were 4.8±2.2 U/L. The ADA levels correlated with CSF proteins, absolute lymphocyte count and the staging of the disease. Using a cut off level of >L10 U/L, CSF ADA had a sensitivity of 92.5% and specificity of 97%. PCR for M. tuberculosis was positive in 12 out of 27 "most likely" TBM cases, 5 out of 27 "unconfirmed" TBM cases and 3 out of 37 controls. PCR for M. tuberculosis had a sensitivity of 44.5% and specificity of 92% in the "most likely" TBM cases.
  
  
  CONCLUSIONS
  ADA is a rapid, inexpensive and sensitive test in the diagnosis of TBM. It is more sensitive than AFB smear and culture. PCR is another rapid test in the diagnosis of TBM with a good specificity, even in those patients already on presumptive anti-tuberculous treatment. However, despite the sensitivity and specificity of CSF ADA, it should be corroborated with AFB smear and CSF PCR.
authors.affiliation: Departments of Neurology.
authors.forename: Fiju
authors.initials: F
authors.lastname: Chacko
authors.affiliation: Departments of Neurology.
authors.forename: Manish
authors.initials: M
authors.lastname: Modi
authors.affiliation: Departments of Neurology.
authors.forename: Vivek
authors.initials: V
authors.lastname: Lal
authors.affiliation: Departments of Neurology.
authors.forename: S
authors.initials: S
authors.lastname: Prabhakar
authors.affiliation: Gastroenterology.
authors.forename: S V
authors.initials: SV
authors.lastname: Rana
authors.affiliation: lmmunopathology Post Graduate Institute of Medical Education and Research, Chandigarh, INDIA.
authors.forename: S K
authors.initials: SK
authors.lastname: Arora
keywords: Adenosine deaminase; PCR; Tubercular meningitis