title: Comparison of latent tuberculosis infection rate between contacts with active tuberculosis and non-contacts.
abstract: BACKGROUND
  Latent tuberculosis infection (LTBI) rate is usually high in contacts with infectious TB patients. In TB-prevalent country, however, background LTBI rate is already high in general population.
  
  
  OBJECTIVE
  To compare the LTBI rate between controls and recognized close contacts.
  
  
  METHODS
  Between February 2010 and January 2014, 183 controls and 376 contacts with TB infection were enrolled. The tuberculin skin test (TST) and QuantiFERON-TB Gold In-Tube (QFT-GIT) were used to diagnose LTBI.
  
  
  RESULTS
  Higher TST positivity was found in the control group than in the contact group (37.7% vs. 29.9%, P = 0.073). The positive QFT-GIT rate was higher in contacts than in controls (32.6% vs. 24.1%, P = 0.054). A significantly higher positive QFT-GIT rate was found in contacts under 30 years of age than in controls (16.1% vs. 0%, P = 0.005).
  
  
  CONCLUSIONS
  In a TB-prevalent country, both TST and QFT-GIT were limited in the diagnosis of recent LTBI in adult contacts probably due to the high background LTBI rate. However, QFT-GIT seems to be better than TST in differentiating LTBI status in contacts younger than 30 year old.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Gyeongsang National University Hospital, Jinju, Gyeongsangnam-do, South Korea.
authors.forename: Jung-Wan
authors.initials: JW
authors.lastname: Yoo
authors.affiliation: Department of Pulmonary and Critical Care Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
authors.forename: Kyung-Wook
authors.initials: KW
authors.lastname: Jo
authors.affiliation: Public Health Center, Hapcheon-gun, Gyeongsangnam-do, South Korea.
authors.forename: Gu Young
authors.initials: GY
authors.lastname: Park
authors.affiliation: Department of Pulmonary and Critical Care Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea. Electronic address: shimts@amc.seoul.kr.
authors.forename: Tae Sun
authors.initials: TS
authors.lastname: Shim
mesh_terms: D000328:Adult; D000368:Aged; D001500:BCG Vaccine / Q000008:administration & dosage / Q000276:immunology; D016358:Contact Tracing / Q000379:methods*; D005260:Female; D006801:Humans; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000635:transmission; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D015995:Prevalence; D056910:Republic of Korea / Q000453:epidemiology; D014374:Tuberculin Test / Q000379:methods; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000635:transmission
chemical_list: D001500:BCG Vaccine
keywords: Close contacts; Latent tuberculosis infection; QuantiFERON(®)-TB Gold In-Tube; Tuberculin skin test