title: Rapid identification of Mycobacterium tuberculosis complex in clinical isolates by combining presumptive cord formation and MPT64 Antigen Immunochromatographic Assay.
abstract: OBJECTIVE
  Combining the results of presumptive cord formation in smear and MPT64 Antigen Immunochromatographic Assay has been suggested to reduce the false negative and positive rates for identification of Mycobacterium tuberculosis (MTB) complex in liquid culture. This study was done to evaluate the clinical utility of combining the results of the two tests for rapid identification MTB complex in mycobacterial isolates.
  
  
  METHODS
  484 isolates of mycobacteria obtained in MGIT culture were identified using presumptive cord formation in smear and further by MPT64 Antigen ICT assay. Result obtained were analyzed taking PNB inhibition test as the reference standard.
  
  
  RESULTS
  Combining the results of the two tests, 464 (95.9%) isolates were correctly identified while discrepant results were obtained in 20 (4.1%) isolates. When the results of the two tests were intersected, the specificity and PPV was 100%, but the sensitivity decreased to 96.4% and the NPV to 68.6%. On the other hand, when the results of the two methods were combined, the sensitivity and NPV was 100%, but the specificity decreased to 88.6% and the PPV to 99.1%.
  
  
  CONCLUSIONS
  Presumptive cord formation and MPT64 antigen ICT assay can be used in combination for identification of MTB complex. When both the test are positive, the culture can be reported to contain MTB complex. If both the tests are negative, the culture should be reported to contain NTM. Only when discrepant results are obtained by the two tests, further evaluation is necessary to ensure an accurate diagnosis.
authors.affiliation: Consultant (Pathology) & HoD, Department of Pathology, Command Hospital (CC), Lucknow, India.
authors.forename: Nikhilesh
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Classified Specialist (Pathology & Microbiology), Command Hospital (CC), Lucknow, India. Electronic address: ash.mhctc@gmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Agarwal
authors.affiliation: Professor and Head, Department of Microbiology, SGPGIMS, Lucknow, India.
authors.forename: T N
authors.initials: TN
authors.lastname: Dhole
authors.affiliation: Professor and Head, Department of Botany, University of Lucknow, Lucknow, India.
authors.forename: Y K
authors.initials: YK
authors.lastname: Sharma
mesh_terms: D000942:Antigens, Bacterial / Q000276:immunology*; D002846:Chromatography, Affinity; D046508:Culture Techniques; D006801:Humans; D009165:Mycobacterium Infections, Nontuberculous / Q000175:diagnosis*; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D009579:Nitrobenzoates; D009170:Nontuberculous Mycobacteria; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D062606:Tertiary Care Centers; D014376:Tuberculosis / Q000175:diagnosis*
chemical_list: D000942:Antigens, Bacterial; C510537:MPT64 protein, Mycobacterium tuberculosis; D009579:Nitrobenzoates; C008629:4-nitrobenzoic acid
keywords: Cord; Immunochromatography; MPT64 Antigen; Mycobacterium tuberculosis complex