Prevalence of tuberculous infection among students in Naples

The aim of this study was to estimate the prevalence of tuberculous (TB) infection in Naples, Italy. The target population was defined as pupils aged 6, 9 and 13 yrs, studying in state and private schools in Naples. A stratified cluster sampling design was used. The stratification criteria were: age (6, 9, 13 yrs); type of school (state or private); and district within the town. Prevalence of TB infection was assessed through a tuberculin Tyne test. Some individual risk factors of tuberculous infection were also investigated by means of a simple questionnaire given to pupils' parents. Among observers reproducibility of test reading was also evaluated. An overall prevalence of TB infection of 5.7% (95% confidence interval (95% CI) 4.6-6.8) was observed in the 1,597 sampled subjects. Skin-test positivity was highly variable with age, ranging from 2.8 (95% CI 1.0-4.6) at 6 yrs to 9.4% (95% CI 7.1-11.7) at 13 yrs. In 458 children (28.7%) response was blindly assessed by three independent observers. Reproducibility of tuberculin skin-test reading was good, with an overall kappa value of 0.718. Only parents' drug abuse was found to be significantly associated with infection. This is the first study to evaluate the prevalence of tuberculous infection in Naples.