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Published on: August 11, 2018
Tuberculin Reactivity in School Age Children; Five-year Follow-up in Iran
Mitra Hemmati1, Keyghobad Ghadiri, Mansour Rezaei
1Infectious Disease Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran.
Insights
Tuberculin skin test (TST) positivity was 8.15% in 7-11 year olds. No active tuberculosis (TB) cases were found during a five-year follow-up, suggesting low TB transmission in this age group.
Area of Science:
- Public Health
- Infectious Diseases
- Pediatrics
Background:
- Tuberculosis (TB) remains a global health concern.
- The Tuberculin Skin Test (TST) is a standard diagnostic tool for TB infection.
- Bacillus Calmette-Guerin (BCG) vaccination can influence TST results.
Purpose of the Study:
- To determine the prevalence of positive TST in primary school children (7-11 years).
- To monitor individuals with positive TST for the development of active TB over five years.
Main Methods:
- A cluster random sample of 10,184 children aged 7-11 years in Kermanshah, Iran, underwent TST.
- Positive TST was defined as an induration of ≥15 mm after 72 hours.
- Test-positive children were followed for five years to detect active TB.
Main Results:
- 8.15% of children had a positive TST (8.7% boys, 7.8% girls).
- A significant linear trend of increasing TST positivity with age was observed (P<0.001).
- No new cases of active TB were identified during the five-year follow-up period.
Conclusions:
- The prevalence of positive TST in this cohort of Iranian primary school children is 8.15%.
- The absence of active TB cases during follow-up suggests limited ongoing transmission in this population.
- These findings contribute to understanding TB epidemiology in school-aged children.
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.
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