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Prevalence of tuberculosis infection in Melbourne secondary school students
P D Johnson1, J B Carlin, C M Bennett
1Clinical Epidemiology and Biostatistics Unit, Royal Children's Hospital, Melbourne, VIC. Paul.Johnson@med.monash.edu.au
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 > or = 5 mm with a history of recent exposure; > or = 10 mm and no prior BCG vaccination; > or = 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% CI, 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.