Prevalence of latent tuberculosis infection and its risk factors in schoolchildren and adolescents in Shanghai, China

Objectives: As tuberculosis (TB) infection in childhood contributes to the pool of individuals with latent tuberculosis infection (LTBI) from which future tuberculosis cases arise, this study aimed to determine the prevalence and risk factors associated with LTBI in schoolchildren and adolescents from Shanghai, China. Methods: In this cross-sectional study, we administered T-SPOT.TB and TB infection risk factor questionnaire to children and adolescents aged between 10 and 18 years in 2010 in Shanghai. LTBI cases were defined by positive T-SPOT.TB test results and X-ray confirmation. Results: A total of 1106 schoolchildren and adolescents were enrolled, of which 46.1% were male, and 91.8% were vaccinated with Bacille Calmette Guerin (BCG). Overall, 52 (4.7%) children had a positive T-SPOT.TB result, with significant increase in age distribution. However, none of the participants demonstrated TB-related abnormality on X-ray examination. Multivariate analysis showed that LTBI was associated with no BCG vaccination (odds ratio: 2.40; 95% confidence interval: 1.182-5.335) and a history of TB exposure (odds ratio: 6.89; 95% confidence interval: 3.095-15.35). For 46 children and adolescents with history of TB exposure, contact hours per week of TB cases were significantly associated with risk of LTBI. Conclusions: Prevalence of LTBI in schoolchildren and adolescents in Shanghai is relatively low compared with other high epidemic areas of TB. A higher risk of LTBI was observed among children with no BCG vaccination and those with a history of TB exposure, which suggests that the prevalence of LTBI among schoolchildren could be further reduced by strengthening BCG vaccination under the national immunization programme and enhancing contact investigation of active TB patients.