Risk factors associated with latent tuberculosis infection in Mexican American children.

OBJECTIVES: To determine risk factors that are associated with the presence of latent tuberculosis infection (LTBI) in Mexican American children.
METHODS: In this prospective cohort study, we administered tuberculin skin tests (TSTs) and a tuberculosis (TB) risk factor questionnaire to children who were aged 1 to 18 years in immigrant families at a Denver inner-city community health center and elementary school-based health center. Information requested on the questionnaire included child demographics, child and parent birth location, Bacille Calmette-Guérin (BCG) vaccination, and a history and the duration of child and family travel to and visitors from countries where TB is endemic. TST results were read at 48 to 72 hours and were interpreted as positive at 5- and 10-mm induration, depending on risk factor history. All participants received $5 coupons on return for TST reading.
RESULTS: Of 584 children enrolled, 96% returned for TST evaluation, median age was 4 years, 48.6% were male, 98.5% were Latino, 66.3% were born in the United States, and 33% were born in Mexico. Overall, 12.4% of children had positive TSTs. For all children in the study, a positive TST was associated with birth in Mexico and no BCG received (adjusted odds ratio [OR]: 15.7; 95% confidence interval [CI]: 1.5-165.2), birth in Mexico and received BCG (adjusted OR: 29; 95% CI: 12.7-66.1), birth in the United States and received BCG (adjusted OR: 9.1; 95% CI: 2.4-34.1), and child travel to Mexico (adjusted OR: 2.8;95% CI: 1.5-5.4). Risk factors for having a positive TST in the 387 children who were born in the United States were travel to Mexico (unable to calculate the OR because all had traveled to Mexico), older age (median: 6 years; adjusted OR: 1.2/year; 95% CI: 1.02-1.40), and a history of BCG vaccination (adjusted OR: 8.2; 95% CI: 2.0-34.0). For the 195 children who were born in Mexico, logistic regression of the following variables showed that none of the variables remained in the model: child age, gender, BCG status, family travel to Mexico, visitors to the United States, child travel to Mexico, years lived in Mexico, and years since BCG.
CONCLUSIONS: In a population of primarily Mexican American children, those who were born in the United States had an increased risk for developing LTBI when they had a history of BCG vaccination or had traveled to Mexico. For children who were born in Mexico, we were unable to identify additional risk factors for the presence of LTBI, besides their birth in Mexico. Incentives for return for TST reading, such as grocery coupons, are highly effective.