title: Early diagnosis of tuberculous meningitis by an indirect ELISA protocol based on the detection of the antigen ESAT-6 in cerebrospinal fluid.
abstract: BACKGROUND
  Early diagnosis of tuberculous meningitis (TBM) is still a challenge; the present study aimed to establish a method of detecting the antigen early secreted antigenic target 6 (ESAT-6) in cerebrospinal fluid (CSF) by an indirect enzyme-linked immunosorbance assay (ELISA) protocol and to study the value of detecting ESAT-6 in CSF in the early diagnosis of TBM.
  
  
  METHODS
  An indirect ELISA protocol was used, employing a monoclonal antibody (mAb) against ESAT-6, which was used to demonstrate ESAT-6 in the CSF from TBM patients and non-TBM controls. CSF was obtained from 100 patients: confirmed TBM, clinically diagnosed TBM, disease controls, and healthy controls (n = 10). Pure recombinant ESAT-6 (standard product) was used in serial dilutions to detect the absorbance and to establish a standard curve from the data; the concentration was on the X axis vs. absorbance on the Y axis, and the standard curve was used to interpolate the concentration of ESAT-6 in samples.
  
  
  RESULTS
  The indirect ELISA method provided 88 % sensitivity and 92 % specificity for the diagnosis of TBM using a mAb to ESAT-6. The mean concentration of ESAT-6 in TBM patients was significantly higher than that of the non-TBM groups. There was also a significant difference in the mean ESAT-6 expression between the confirmed TBM patients and the clinically diagnosed TBM patients (p < 0.01).
  
  
  CONCLUSIONS
  Detection of ESAT-6 in the CSF of TBM patients by indirect ELISA protocol gives a reliable early diagnosis and can be used to develop an immunodiagnostic assay with increased sensitivity and specificity.
authors.affiliation: Department of Neurology, Yantai Yuhuangding Hospital, Yantai, 264000, Shandong Province, China.
authors.forename: F
authors.initials: F
authors.lastname: Song
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Nai
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial / Q000134:cerebrospinal fluid* / Q000276:immunology; D001426:Bacterial Proteins / Q000134:cerebrospinal fluid* / Q000276:immunology; D015415:Biomarkers / Q000134:cerebrospinal fluid; D002138:Calibration; D016022:Case-Control Studies; D042241:Early Diagnosis; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012015:Reference Standards; D014390:Tuberculosis, Meningeal / Q000134:cerebrospinal fluid / Q000175:diagnosis*; D015854:Up-Regulation; D055815:Young Adult
chemical_list: D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D015415:Biomarkers; C093276:ESAT-6 protein, Mycobacterium tuberculosis