title: Comparison of an interferon-gamma release assay and the tuberculin skin test for diagnosis of latent tuberculosis in homeless people in Iran: a cross-sectional study.
abstract: BACKGROUND
  The aim of this study was to evaluate of the concordance between the results of the tuberculin skin test (TST) and an interferon-γ release assay (QuantiFERON test, QFT-GIT) for diagnosis of latent tuberculosis infection (LTBI) in homeless people in Tehran city, Iran.
  
  
  METHODS
  This cross-sectional study was conducted from June to August 2012. Homeless people were eligible to participate in the study if they were 18-60 years old.
  
  
  RESULTS
  Among 569 homeless people, 46.22% (95% confidence interval (CI) = 42.16-50.33%) and 20.39% (95% CI = 17.28-23.9%) were QFT-GIT and TST positive, respectively. Among these participants, the prevalence of LTBI with positivity of at least one of the tests was 52.2%. The overall agreement between QFT-GIT and TST was 62.21% (kappa = 0.21, 95% CI = 0.13-0.29, p < 0.001). Factors associated with positive results in QFT-GIT and TST were older age, being male, having a longer history of homelessness and having a history of incarceration in the last 10 years.
  
  
  CONCLUSIONS
  A high prevalence of LTBI was seen among homeless people in this study. There was a poor concordance between QFT-GIT and TST among this group. To better assess the utility of QFT-GIT in detection of LTBI further studies with a low prevalence of LTBI in this group are recommended.
authors.affiliation: From the Department of Epidemiology, Pasteur Institute of Iran , Tehran.
authors.forename: Fahimeh
authors.initials: F
authors.lastname: Bagheri Amiri
authors.forename: Mahnaz
authors.initials: M
authors.lastname: Saifi
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Gouya
authors.forename: Mahdi
authors.initials: M
authors.lastname: Rohani
authors.forename: Ehasn
authors.initials: E
authors.lastname: Mostafavi
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006703:Ill-Housed Persons; D006801:Humans; D059425:Interferon-gamma Release Tests; D007492:Iran / Q000453:epidemiology; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D014374:Tuberculin Test; D055815:Young Adult
keywords: Latent tuberculosis; QuantiFERON; concordance; homeless; tuberculin skin test