Two-step tuberculin skin test and booster phenomenon prevalence among Brazilian medical students
Authors: Teixeira, E.G.1; Kritski, A.2; Ruffino-Netto, A.3; Steffen, R.4; Lapa e Silva, J.R.2; Belo, M.5; Luiz, R.R.2; Menzies, D.6; Trajman, A.7
Source: The International Journal of Tuberculosis and Lung Disease, Volume 12, Number 12, December 2008 , pp. 1407-1413(7)
Publisher: International Union Against Tuberculosis and Lung Disease
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
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