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Tuberculin response in indigenous Warao children in Venezuela; BCG vaccination doesn't affect the positive rates

Abstract number: P1562

Maes M., Del Nogal B., Fernández de Larrea C., Segovia Y., de Waard J.H.

Background: The in vitro interferon-gamma (IFN-gamma) assay has emerged as a more specific alternative to the tuberculin skin test (TST) for the diagnosis of latent tuberculosis (TB) infection in BCG vaccinated persons. However, to justify the introduction of this new and expensive test, studies in low-income countries must show that BCG vaccination significantly affects the TST results.

Objective: To determine the specificity of the TST is diminished in BCG vaccinated children from a high TB incidence, indigenous Warao population in Venezuela.

Methods: 1479 children, 1–15 years of age, from different Warao communities were tested using 2 TU RT 23 tuberculin. Reactions were measured at 48 hours. The presence of the BCG scar and age of the child was recorded. A reaction of 10 mm or more was considered as positive. The Kruskal-Wallis and the Pearson test were conducted for the analysis of the results.

Results: 1088 children in this study had a BCG scar and 391 children did not. The age distribution in both groups was not significantly different. A positive TST was found in 10.8% of the BCG vaccinated and 8.5% of the non-vaccinated children, a difference that was not statistically significant. In both groups a positive TST was strongly related with the age of the child and there was no significant difference of TST positive in the same age groups of the vaccinated and non-vaccinated children.

Conclusion: In this study BCG vaccination does not significantly affect the results of the TST test and is cheaper and easier to perform than the interferon gamma test. The TST test is still a valuable tool for detecting tuberculosis infection, especially in this rural setting. In a future study we will determine whether there is a significant difference in the sensitivity of the two tests for the Warao population.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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