Two-step tuberculin skin test and booster phenomenon prevalence among Brazilian medical students (original) (raw)
Related papers
Clinical Microbiology and Infection, 2004
The relationship of age and previous BCG vaccination with tuberculin skin test (TST) reactivity was investigated to assess the interpretation of TST results in the adult population of Turkey, where there is a high prevalence of tuberculosis and a routine BCG vaccination programme. The influences of age and BCG vaccine status on booster reaction were also evaluated. TST was applied (5 tuberculin units of purified protein derivative intradermally) to two healthy adult groups, namely 98 medical students and 187 elderly people in a retirement home. The TST was considered positive if an induration ‡ 10 mm in diameter was produced. Subjects (41 elderly people and 39 students) with a reaction < 10 mm in diameter were retested 1 week later. There was no significant difference between the students (59.1%) and elderly subjects (58.8%) with respect to positive TST response. No influence of BCG scars on TST reactivity was observed in either group. The booster effect was seen more commonly in the elderly, but the presence of a BCG scar did not influence the booster effect in either group. It was concluded that a positive TST response and booster reaction in adults in high-prevalence countries may be caused by latent tuberculosis rather than previous vaccination.
Tuberculin reactivity in a population of schoolchildren with high BCG vaccination coverage
Revista Panamericana De Salud Publica-pan American Journal of Public Health, 2003
Methods. We conducted tuberculin skin testing and BCG scar reading in 1148 children aged 7-14 years old in the city of Salvador, Bahia, Brazil. We measured the positive effect of the presence of one or two BCG scars on the proportion of tuberculin skin test results above different cut-off levels (induration sizes of ≥ 5 mm, ≥ 10 mm, and ≥ 15 mm) and also using several ranges of induration size (0, 1-4, 5-9, 10-14, and ≥ 15 mm). We also measured the effects that age, gender, and the school where the child was enrolled had on these proportions. Results. The proportion of tuberculin results ≥ 10 mm was 14.2% (95% confidence interval (CI) = 8.0%-20.3%) for children with no BCG scar, 21.3% (95% CI = 18.5%-24.1%) for children with one BCG scar, and 45.0% (95% CI = 32.0%-58.0%) for children with two BCG scars. There was evidence for an increasing positive effect of the presence of one and two BCG scars on the proportion of results ≥ 5 mm and ≥ 10 mm. Similarly, there was evidence for an increasing positive effect of the presence of one and two scars on the proportion of tuberculin skin test results in the ranges of 5-9 mm and of 10-14 mm. The BCG scar effect on the proportion of results ≥ 5 mm and ≥ 10 mm did not vary with age. There was no evidence for BCG effect on the results ≥ 15 mm.
Archives of Internal Medicine, 2001
Background: We estimated the effect of remote BCG vaccination on tuberculin reactivity and the booster effect among hospital employees. Methods: Cross-sectional survey at a university hospital. All personnel employed during a 24-month period were included in the study. Employees were administered 2-step tuberculin testing, and BCG vaccination scars were verified. Results: Of 665 hospital employees studied, 239 (36%) had been vaccinated with BCG in childhood. Significant tuberculin reactions (Ն5 mm) were more frequent among BCG-vaccinated (60%) than among nonvaccinated (29%) employees (odds ratio [OR], 3.6; 95% confidence interval [CI], 2.6-5.2). The predictive value of tuberculosis infection increased with increasing reaction size and greater age (from 37% in subjects 30 years or younger with indurations Ն5 mm to 100% in subjects 50 years or older with indurations Ն15 mm). Among 374 employees with a negative tuberculin test reaction who underwent a second test, 39 (43%) of 91 vaccinated subjects had a positive booster reaction in contrast to 51 (22%) of 232 nonvaccinated subjects (OR, 3.4; 95% CI, 2-5.7). Neither different size criteria nor different definitions of the booster effect had an impact on the predictive value of tuberculosis infection. Conclusions: Remote BCG vaccination largely influences the tuberculin reaction and the boosting phenomenon among hospital employees. The interpretation of the results of 2-step tuberculin testing in a BCGvaccinated subject must take into account age, size of the reaction, and local prevalence of tuberculosis infection. No single criterion, however, can accurately separate reactions caused by true infection from those caused by BCG vaccination.
Journal of Tropical Pediatrics, 2004
This case-control study analyses the association between the tuberculin response and the neonatal BCG vaccine in 330 children under 15 who are home contacts of tuberculosis patients, taking into account risk factors for the transmission of infection. Interviews were conducted with 330 children, their parents or legal guardians. Chest X-rays were taken and the tuberculin test (TT) applied using 0.1 ml of PPD RT23, taking an induration reading of ≥10mm as the cutoff point for a positive test result. Prior BCG vaccination was ascertained by observing the presence of a scar on the deltoid region of the right arm. Six children were excluded because they had signs/symptoms of pulmonary tuberculosis, thereby reducing the final sample to 324 children. The multivariate analysis showed that being exposed to a patient with pulmonary lesions with cavities (OR = 3.14; CI: 1.59-6.20; p = 0.000), a positive sputum smear (OR = 3.65; CI: 1.52-8.78; p = 0.002) or a positive culture (OR = 4.42; CI: 1.39-14.1; p = 0.005), being under five (OR = 0.47; CI: 0.22-0.99; p = 0.045) are independently associated with a positive TT. The fact that a prior BCG scar is not associated with a positive response to the TT indicates the need to reopen discussion of the guidelines which exist in many poor countries where tuberculosis is still a serious public health problem. Such guidelines include those issued by the Brazilian Ministry of Health, which considers the child under 15 in contact with a tuberculosis case to be infected only if there is a TT of 10 mm or more and the child received no prior BCG vaccination.
BMC Public Health, 2007
Background Assuming a higher risk of latent tuberculosis (TB) infection in the population of Rio de Janeiro, Brazil, in October of 1998 the TB Control Program of Clementino Fraga Filho Hospital (CFFH) routinely started to recommend a two-step tuberculin skin test (TST) in contacts of pulmonary TB cases in order to distinguish a boosting reaction due to a recall of delayed hypersensitivity previously established by infection with Mycobacterium tuberculosis (M.tb) or BCG vaccination from a tuberculin conversion. The aim of this study was to assess the prevalence of boosted tuberculin skin tests among contacts of individuals with active pulmonary tuberculosis (TB). Methods Retrospective cohort of TB contacts ≥ 12 years old who were evaluated between October 1st, 1998 and October 31st 2001. Contacts with an initial TST ≤ 4 mm were considered negative and had a second TST applied after 7–14 days. Boosting reaction was defined as a second TST ≥ 10 mm with an increase in induration ≥ 6 mm ...
2007
Bacille Calmette-Guérin (BCG) vaccination can confound tuberculin skin test (TST) reactions in the diagnosis of latent tuberculosis infection (LTBI). The TST was compared with a Mycobacterium tuberculosis (MTB)-specific enzyme-linked immunospot (ELISPOT) assay during an outbreak of MTB infection at a police academy in Germany. Participants were grouped according to their risk of LTBI in close (n536) or occasional (n5333) contacts to the index case. For the TST, the positive response rate was 53% (19 out of 36) among close and 16% (52 out of 333) among occasional contacts. In total, 56 TST-positive contacts (56 out of 71578.9%) and 27 TST-negative controls (27 out of 29859.1%) underwent ELISPOT testing. The odds ratio (OR) of a positive test result across the two groups was 29.2 (95% confidence interval (CI) 3.5-245.0) for the ELISPOT and 19.7 (95% CI 2.0-190.2) for the TST with a 5 mm cutoff. Of 369 contacts, 158 (42.8%) had previously received BCG vaccination. The overall agreement between the TST and the ELISPOT was low, and positive TST reactions were confounded by BCG vaccination (OR 4.8 (95% CI 1.3-18.0)). In contrast, use of a 10-mm induration cutoff for the TST among occasional contacts showed strong agreement between TST and ELISPOT in nonvaccinated persons. In bacille Calmette-Guérin-vaccinated individuals, the Mycobacterium tuberculosis-specific enzyme-linked immunospot assay is a better indicator for the risk of latent tuberculosis infection than the tuberculin skin test.