title: A diagnostic accuracy study of Xpert®MTB/RIF in HIV-positive patients with high clinical suspicion of pulmonary tuberculosis in Lima, Peru.
abstract: BACKGROUND
  Diagnosis of pulmonary tuberculosis (TB) among human immunodeficiency virus (HIV) patients remains complex and demands easy to perform and accurate tests. Xpert®MTB/RIF (MTB/RIF) is a molecular TB diagnostic test which is rapid and convenient; the test requires minimal human resources and reports results within two hours. The majority of performance studies of MTB/RIF have been performed in high HIV burden settings, thus TB diagnostic studies among HIV patients in low HIV prevalence settings such as Peru are still needed.
  
  
  RESULTS
  From April 2010 to May 2011, HIV-positive patients with high clinical suspicion of TB were enrolled from two tertiary hospitals in Lima, Peru. Detection of TB by MTB/RIF was compared to a composite reference standard Löwenstein-Jensen (LJ) and liquid culture. Detection of rifampicin resistance was compared to the LJ proportion method. We included 131 patients, the median CD4 cell count was 154.5 cells/mm(3) and 45 (34.4%) had TB. For TB detection among HIV patients, sensitivity of MTB/RIF was 97.8% (95% CI 88.4-99.6) (44/45); specificity was 97.7% (95% CI 91.9-99.4) (84/86); the positive predictive value was 95.7% (95% CI 85.5-98.8) (44/46); and the negative predictive value, 98.8% (95% CI 93.6-99.8) (84/85). MTB/RIF detected 13/14 smear-negative TB cases, outperforming smear microscopy [97.8% (44/45) vs. 68.9% (31/45); p = 0.0002]. For rifampicin resistance detection, sensitivity of MTB/RIF was 100% (95% CI 61.0-100.0) (6/6); specificity was 91.0% (95% CI 76.4-96.9) (30/33); the positive predictive value was 66.7% (95% CI 35.4-87.9) (6/9); and the negative predictive value was 100% (95% CI 88.7 -100.0) (30/30).
  
  
  CONCLUSIONS
  In HIV patients in our population with a high clinical suspicion of TB, MTB/RIF performed well for TB diagnosis and outperformed smear microscopy.
authors.affiliation: Facultad de Medicina Alberto Hurtado, Universidad Peruana Cayetano Heredia, Lima, Peru. gabriela.carriquiry.c@upch.pe
authors.forename: Gabriela
authors.initials: G
authors.lastname: Carriquiry
authors.forename: Larissa
authors.initials: L
authors.lastname: Otero
authors.forename: Elsa
authors.initials: E
authors.lastname: González-Lagos
authors.forename: Carlos
authors.initials: C
authors.lastname: Zamudio
authors.forename: Eduardo
authors.initials: E
authors.lastname: Sánchez
authors.forename: Pamela
authors.initials: P
authors.lastname: Nabeta
authors.forename: Miguel
authors.initials: M
authors.lastname: Campos
authors.forename: Juan
authors.initials: J
authors.lastname: Echevarría
authors.forename: Carlos
authors.initials: C
authors.lastname: Seas
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gotuzzo
mesh_terms: D000995:Antitubercular Agents / Q000627:therapeutic use; D015658:HIV Infections / Q000150:complications*; D006801:Humans; D010568:Peru / Q000453:epidemiology; D012293:Rifampin / Q000627:therapeutic use; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology
chemical_list: D000995:Antitubercular Agents; D012293:Rifampin