Prevalence of tuberculosis infection in Melbourne secondary school students

Objective: To estimate the prevalence of asymptomatic Mycobacterium tuberculosis infection in Melbourne secondary school students. Design: Cross-sectional Mantoux testing of a partly random and partly targeted sample of secondary school students, designed to enable estimation of prevalence by region of birth. Setting: Fifty-one State and Catholic secondary schools in metropolitan Melbourne during 1995. Participants: Australian and overseas-born students in Years 9 and 10. Outcome measures: Proportions of students with positive Mantoux reactions (defined as induration at 48 hours of greater than or equal to 5 mm with a history of recent exposure; greater than or equal to 10 mm and no prior BCG vaccination; greater than or equal to 15 mm and prior BCG vaccination). Results: Of 2586 students potentially eligible for testing, evaluable results were obtained from 1274 (49%). The overall prevalence of infection for Melbourne students in Years 9 and 10 was 2.5% (95% Cl, 1.1-3.9%). Main predictors of a positive test were birth overseas and number of years residing overseas. Prevalence varied considerably by region of birth, and was very low in students born in Australia (0.7%), "other developed countries" (0.7%), and Southern Europe (0). The highest rates were observed in students born in Indochina (15.9%), other countries in South East Asia (10.2%), and Eastern Europe (10.2%). Conclusions: The risk of a young person becoming infected with M. tuberculosis while living in Melbourne is very low. Our results do not indicate a need for the reintroduction of mass screening in Victorian schools. If targeted screening were to be considered, the group most likely to benefit would be recently arrived migrants from Indochina.