Age-specific cut-offs for the tuberculin skin test to detect latent tuberculosis in BCG-vaccinated children

Int J Tuberc Lung Dis. 2008 Dec;12(12):1401-6.


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).

Design: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Age Factors
  • BCG Vaccine*
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Tuberculin Test*
  • Tuberculosis / diagnosis*
  • Vaccination


  • BCG Vaccine