title: Comparison of an adenosine deaminase assay with ELISA for the diagnosis of tuberculous meningitis infection.
abstract: BACKGROUND
  Diagnosing tuberculous meningitis (TBM) remains problematic despite many new advanced diagnostic methods. Adenosine deaminase (ADA) assays have emerged as novel alternatives to other costly and time-consuming methods for TBM diagnosis. In the present study the usefulness of the ADA method was assessed for the diagnosis of TBM and compared with an in-house developed ELISA method for detecting the antigen 85 (Ag 85) complex of M. tuberculosis in cerebrospinal fluid (CSF) samples of suspected and culture-confirmed TBM patients.
  
  
  METHODS
  ADA activity in CSF was determined at 37 degrees C according to the method of Guisti and Galanti. ELISA, employing monoclonal antibodies against the purified Ag 85 complex, was used to demonstrate Ag 85 complex in CSF from TBM patients. CSF samples were obtained from 153 patients in three different groups: confirmed TBM (n=27), clinically suspected TBM (n=39), and non-TBM (n=87).
  
  
  RESULTS
  The ADA method yielded sensitivity and specificity of 83% and 86%, which are similar to those of the ELISA method (89% and 90%). The correlation between the Ag 85 complex activity in absorbance by ELISA and the ADA activity obtained in units per liter per minute (U/l/min) was also positive and significant. (Pearson's correlation coefficient r=0.3234, 95%CI: 0.1621-0.4679, p<0.001).
  
  
  CONCLUSIONS
  This study suggests that the ADA method can be performed for TBM diagnosis in low-income TB-affected regions where more sophisticated facilities are generally not available.
authors.affiliation: Biochemistry Research Laboratory, Central India Institute of Medical Sciences, Nagpur, India.
authors.forename: Rajpal S
authors.initials: RS
authors.lastname: Kashyap
authors.forename: Sonali P
authors.initials: SP
authors.lastname: Ramteke
authors.forename: Poonam S
authors.initials: PS
authors.lastname: Deshpande
authors.forename: Hemant J
authors.initials: HJ
authors.lastname: Purohit
authors.forename: Girdhar M
authors.initials: GM
authors.lastname: Taori
authors.forename: Hatim F
authors.initials: HF
authors.lastname: Daginawala
mesh_terms: D000243:Adenosine Deaminase / Q000134:cerebrospinal fluid* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D014390:Tuberculosis, Meningeal / Q000134:cerebrospinal fluid / Q000175:diagnosis* / Q000201:enzymology*
chemical_list: D000243:Adenosine Deaminase