title: [Effectiveness of interferon-gamma release assays in the tuberculosis contact investigation of elderly people].
abstract: OBJECTIVE
  To confirm the effectiveness of interferon-gamma release assays (IGRAs) in the tuberculosis (TB) contact investigation of elderly people, we analyzed the results of the QuantiFERON TB Gold in tube (QFT-3G) test, which is a commercially available IGRA.
  
  
  METHODS
  We analyzed the results of the QFT-3G test in 2,420 subjects who were in close contact with TB patients. We investigated subjects with latent TB infection and those showing the onset of TB among the QFT-3G-positive subjects.
  
  
  RESULTS
  The QFT-3G-positive rate was 7.3% (95% confidence interval, 6.2%-8.3%). In addition, we demonstrated that the QFT-3G-positive rate increased with age (P < 0.001).
  
  
  CONCLUSIONS
  The QFT-3G-positive rate was high, particularly in elderly people (> or = 60 years), but the rate was significantly lower than the predicted prevalence of TB infection. Therefore, it was assumed that the QFT-3G test does not always provide a positive result, even in cases of subjects with a previous TB infection. Furthermore, data from the QFT-3G-positive subjects indicated that approximately one half of subjects aged 60-69 years, approximately one-third of those aged 70-79 years, and approximately one-quarter of those aged over 80 years have had recent TB infections. In conclusion, the results of the QFT-3G test in elderly people need to be carefully evaluated according to the contact situation with TB patients; nevertheless, the QFT-3G test is useful for the screening of latent TB infection in elderly people who were in close contact with TB patients.
authors.forename: Junji
authors.initials: J
authors.lastname: Seto
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Ahiko
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016358:Contact Tracing / Q000379:methods*; D006801:Humans; D059425:Interferon-gamma Release Tests; D008875:Middle Aged; D014376:Tuberculosis / Q000635:transmission*