Introduction: The frequency of tuberculosis infection, particularly among children, indicates the magnitude of the disease reservoir. The aim of this study was to ascertain the prevalence of tuberculosis infection in children in the Autonomous Community of Madrid and its association with social class.
Material and methods: We performed a cross sectional study of 6-year-old schoolchildren living in the Autonomous Community of Madrid, selected through probabilistic sampling. From September 1999 through June 2000, information was collected on residence stratum, tuberculin test (positivity threshold 5 mm), social class (five categories), based on the occupation of the main earner in the family, and the formal education attained by the parents. We calculated 95% confidence intervals for the prevalence estimates according to a Poisson distribution.
Results: A total of 2,721 children were studied. The prevalence of tuberculosis infection for the total study population was 0.62% (95% CI: 0.29-0.95). The prevalence of tuberculosis infection was 0.42% (95% CI: 0.00-0.85) in social class I (the highest), 0.00% (95% CI: 0.00-1.17) in class II, 0.77% (95% CI: 0.00-1.86) in class III, 0.62% (95% CI: 0.00-1.32) in class IV, and 1.57% (95% CI: 0.00-3.40) in class V (the lowest). In both fathers and mothers, the highest prevalence of tuberculosis infection was found in the group that had only completed elementary school or basic general education (up to the age of 14).
Conclusions: The prevalence of tuberculosis infection in the Autonomous Community of Madrid is similar to that in others areas of Spain. The results of our study are consistent with a lower prevalence in the higher socioeconomic groups.