title: Tuberculin skin test and boosted reactions among newly employed healthcare workers: an observational study.
abstract: OBJECTIVE
  To evaluate the prevalence of and factors associated with latent tuberculosis infection (LTBI) based on the tuberculin skin test (TST) and to estimate the boosted reaction rate among newly employed healthcare workers (HCWs).
  
  
  METHODS
  Newly employed HCWs between January 2010 and July 2012 at Severance Hospital in South Korea were enrolled in this study. A one-step TST was conducted before October 2011, and a two-step TST after October 2011.
  
  
  RESULTS
  Of 2132 participants, 778 (36.5%) had positive TST results. Being older (odds ratio [OR] 1.10, 95% confidence interval [CI] 1.06-1.13, P<0.001), male (OR 1.78, 95% CI 1.21-2.62, P = 0.003), rejoining the hospital workforce (OR 1.58, 95% CI 1.04-2.40, P = 0.032), and having a previous history of tuberculosis (TB) (OR 18.21, 95% CI 2.15-154.10, P = 0.008) during the one-step period, and being older (OR 1.15, 95% CI 1.10-1.21, P<0.001) during the two-step period were significantly associated with a positive TST. A two-step TST was performed in 556 HCWs, and a boosted reaction was observed in 79 (14.2%). The induration size on the first TST (5-9-mm group) was the only factor associated with a boosted reaction on the second TST.
  
  
  CONCLUSIONS
  The prevalence of LTBI based on the TST among newly employed HCWs was high. The boosted reaction rate on two-step TST was not low; therefore, the use of two-step TST may be necessary for regular monitoring in countries with an intermediate TB burden and a high rate of Bacillus Calmette-Guérin vaccination.
authors.affiliation: Division of Pulmonology, Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Song Yee
authors.initials: SY
authors.lastname: Kim
authors.forename: Moo Suk
authors.initials: MS
authors.lastname: Park
authors.forename: Young Sam
authors.initials: YS
authors.lastname: Kim
authors.forename: Se Kyu
authors.initials: SK
authors.lastname: Kim
authors.forename: Joon
authors.initials: J
authors.lastname: Chang
authors.forename: Dongeun
authors.initials: D
authors.lastname: Yong
authors.forename: Hyun Sook
authors.initials: HS
authors.lastname: Kim
authors.forename: Kyungwon
authors.initials: K
authors.lastname: Lee
authors.forename: Young Ae
authors.initials: YA
authors.lastname: Kang
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006282:Health Personnel; D006801:Humans; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D014374:Tuberculin Test; D055815:Young Adult