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Free Content Two-step tuberculin skin test and booster phenomenon prevalence among Brazilian medical students

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Abstract:

SETTING: Five medical schools in three cities in Rio de Janeiro State, Brazil, with different tuberculosis (TB) incidence rates.

OBJECTIVE: To evaluate the prevalence of the booster phenomenon and its associated factors in a young universally BCG-vaccinated TB-exposed population.

DESIGN: A two-step tuberculin skin test (TST) was performed among undergraduate medical students. Boosting was defined as an induration ≥10 mm in the second TST (TST2), with an increase of at least 6 mm over the first TST (TST1). The association of boosting with independent variables was evaluated using multivariate analysis.

RESULTS: Of the 764 participants (mean age 21.9 ± 2.7 years), 672 (87.9%) had a BCG scar. The overall booster phenomenon prevalence was 8.4% (95%CI 6.5–10.6). Boosting was associated with TST1 reactions of 1–9 mm (aOR 2.5, 95%CI 1.04–5.9) and with BCG vaccination, mostly after infancy, i.e., after age two years (aOR 9.1, 95%CI 1.2–70.7).

CONCLUSION: The prevalence of the booster phenomenon was high. A two-step TST in young BCG-vaccinated populations, especially in those with TST1 reactions of 1–9 mm, can avoid misdiagnosis as a false conversion and potentially reduce unnecessary treatment for latent TB infection.

Keywords: BCG; booster; medical students; tuberculin test; tuberculosis

Document Type: Regular Paper

Affiliations: 1: Gama Filho University, Rio de Janeiro, Rio de Janeiro, Brazil; Souza Marques Foundation, Rio de Janeiro, Rio de Janeiro, Brazil; Rio de Janeiro Federal University, Rio de Janeiro, Rio de Janeiro, Brazil 2: Rio de Janeiro Federal University, Rio de Janeiro, Rio de Janeiro, Brazil 3: Ribeirão Preto School of Medicine, São Paulo University, Ribeirao Preto, São Paulo, Brazil 4: Souza Marques Foundation, Rio de Janeiro, Rio de Janeiro, Brazil 5: Gama Filho University, Rio de Janeiro, Rio de Janeiro, Brazil; Souza Marques Foundation, Rio de Janeiro, Rio de Janeiro, Brazil 6: Montreal Chest Institute, McGill University, Montreal, Quebec, Canada 7: Gama Filho University, Rio de Janeiro, Rio de Janeiro, Brazil

Publication date: December 1, 2008

More about this publication?
  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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