Authors: Chan, P-C.1; Chang, L-Y.2; Wu, Y-C.3; Lu, C-Y.i.2; Kuo, H-S.3; Lee, C-Y.2; Huang, L-M.2; Chen, C-J.4
Source: The International Journal of Tuberculosis and Lung Disease, Volume 12, Number 12, December 2008 , pp. 1401-1406(6)
Publisher: International Union Against Tuberculosis and Lung Disease
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.
Keywords: tuberculin skin test; BCG; infants and children; latent tuberculosis infection
Document Type: Regular paper
Affiliations: 1: Centers for Disease Control, Department of Health, Taipei, Taiwan; Graduate Institute of Epidemiology, National Taiwan University, Taipei, Taiwan; Department of Paediatrics, National Taiwan University Hospital and College of Medicine, National Ta 2: Department of Paediatrics, National Taiwan University Hospital and College of Medicine, National Taiwan University, Taipei, Taiwan 3: Centers for Disease Control, Department of Health, Taipei, Taiwan 4: Graduate Institute of Epidemiology, National Taiwan University, Taipei, Taiwan; Genomics Research Centre, Academia Sinica, Taipei, Taiwan