Tuberculin Reactivity in School Age Children; Five-year Follow-up in Iran

Objective: tuberculosis (tb) is an important infectious disease worldwide. tuberculin skin test (tst) is the standard test for diagnosis of tuberculosis infection; bacillus calmette-guerin (bcg) vaccination at birth has effects on this test. the aim of this study was to determine the prevalence of positive tst cases among 7- to 11-year-old primary school children and also to follow test-positive individuals for a five-year period. methods: tst was performed on 10.184 children aged 7-11 years sampled by cluster random method in kermanshah, west iran. those who had a positive test result (i.e. an induration of ≥15 mm following 72 hours of injecting 0.1 ml of 5 tuberculin units of purified protein derivative from mycobacterium tuberculosis) were followed for five years to determine the presence of active tb. also tuberculin positive rates at cut-off points of 10 mm and ≥15 mm for boys and girls and at different ages were derived and compared using the chi-squared test. findings: of 10.184 studied subjects, 830 (8.15%) cases showed positive tst. this rate was 8.7% in boys and 7.8% in girls (p=0.1). a significant linear trend was found between the tuberculin positive rates and age at all cut-off points (p<0.001). no active tb was detected during 5-year follow-up. conclusion: the rate of positive tst cases in primary school children in kermanshah, iran was 8.15% with no new cases of active tuberculosis detection within five-year follow-up.