title: Age-specific cut-offs for the tuberculin skin test to detect latent tuberculosis in BCG-vaccinated children.
abstract: OBJECTIVE
  To evaluate the effect of neonatal vaccination with bacille Calmette-Guérin (BCG) on tuberculin skin test (TST) reactivity over time and to define the optimal age-specific induration cut-offs to detect latent tuberculosis infection (LTBI).
  
  
  METHODS
  TSTs were performed on 783 children aged 3 months to 14 years who had received neonatal BCG. The estimated annual risk of LTBI was derived from TSTs administered to 2504 children aged 7 years who lacked BCG scars. Goodness-of-fit analysis was used to determine the optimal age-specific cut-off values.
  
  
  RESULTS
  The effect of neonatal BCG on TST induration waned with age, reaching a nadir at age 6-7 years. This was followed by a rise in TST reactivity. The optimal age-specific TST cut-off values for the detection of LTBI was estimated to be respectively 21, 18, 13 and 10 mm at ages 0-1, 2-3, 4-5 and 6-7 years. There was a close correlation between these new cut-off values with the estimated risk of LTBI for the first 7 years of life (r = 0.93, P < 0.001).
  
  
  CONCLUSIONS
  The effect of neonatal BCG on TST gradually declines over the first 7 years of life. Our proposed new age-specific TST induration cut-off values could help differentiate between response to BCG and LTBI in young children.
authors.affiliation: Centers for Disease Control, Department of Health, Taipei, Taiwan.
authors.forename: P-C
authors.initials: PC
authors.lastname: Chan
authors.forename: L-Y
authors.initials: LY
authors.lastname: Chang
authors.forename: Y-C
authors.initials: YC
authors.lastname: Wu
authors.forename: C-Yi
authors.initials: CY
authors.lastname: Lu
authors.forename: H-S
authors.initials: HS
authors.lastname: Kuo
authors.forename: C-Y
authors.initials: CY
authors.lastname: Lee
authors.forename: L-M
authors.initials: LM
authors.lastname: Huang
authors.forename: C-J
authors.initials: CJ
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001500:BCG Vaccine; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D014374:Tuberculin Test; D014376:Tuberculosis / Q000175:diagnosis*; D014611:Vaccination
chemical_list: D001500:BCG Vaccine