title: Evaluation of GeneXpert MTB/RIF for the detection of Mycobacterium tuberculosis and resistance to rifampin in clinical specimens.
abstract: OBJECTIVE
  GeneXpert (GX) is a novel real-time polymerase chain reaction assay for the simultaneous detection of Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF). We evaluated the performance of GX for direct detection of MTB in respiratory and non-respiratory specimens and assessed the ability of the assay to detect resistance to RIF in non-tuberculosis (TB) endemic country.
  
  
  METHODS
  We analyzed 595 clinical samples in a 1550-bed tertiary hospital in Madrid, Spain. Specimens were processed using GX, auramine smear, conventional culture, and drug phenotypic susceptibility testing (DST) with MGIT SIRE (BD).
  
  
  RESULTS
  Of the 595 clinical samples, 305 (51.3%) were non-respiratory and 290 (48.7%) were respiratory. In total, MTB was isolated in 81 specimens, 71 of which were positive with GX. The sensitivity, specificity, PPV, and NPV of the GX were: 97.1%, 98.6%, 95.7% and 99.1% for respiratory samples and 33.3%, 99.7%, 80.0% and 97.3% for non-respiratory. GX detected 8 RIF-resistant samples, but only 5 were confirmed by DST.
  
  
  CONCLUSIONS
  GX is an accurate, easy-to-apply and rapid test to detect MTB, especially in smear-positive respiratory samples. Although is a useful tool for the rapid identification of RIF-resistant MTB strains, the rifampin resistant results should be confirmed by DST.
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain. Electronic address: eleonorabunsow@hotmail.com.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Bunsow
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Spain.
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Ruiz-Serrano
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain.
authors.forename: Paula
authors.initials: P
authors.lastname: López Roa
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain.
authors.forename: Martha
authors.initials: M
authors.lastname: Kestler
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Spain.
authors.forename: Dario Garcia
authors.initials: DG
authors.lastname: Viedma
authors.affiliation: Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain; Facultad de Medicina, Universidad Complutense de Madrid, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Bouza
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001431:Bacteriological Techniques / Q000379:methods; D024881:Drug Resistance, Bacterial; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000302:isolation & purification*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012293:Rifampin / Q000494:pharmacology*; D013030:Spain; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D012293:Rifampin
keywords: GeneXpert; Molecular diagnosis; Rifampin-resistant; Tuberculosis