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Tuberculin skin test survey in a pediatric population with high BCG vaccination coverage -- Botswana, 1996
Insights
The tuberculin skin test (TST) is a useful tool for diagnosing pediatric tuberculosis (TB) in Botswana. Most positive TST results in children were due to TB infection, not BCG vaccination.
Area of Science:
- Pediatrics
- Infectious Diseases
- Immunology
Background:
- Tuberculosis (TB) is a leading infectious cause of death globally.
- Diagnosing pediatric TB is challenging, often relying on clinical judgment, chest radiography, and the tuberculin skin test (TST).
- TST interpretation can be complicated by Bacille Calmette-Guérin (BCG) vaccination or exposure to non-tuberculous mycobacteria, while factors like HIV and malnutrition can suppress TST response.
Purpose of the Study:
- To assess the utility of the TST for diagnosing pediatric TB in a population with high BCG vaccination coverage.
- To determine if positive TST results in children in Botswana are more likely due to TB infection or prior BCG vaccination.
Main Methods:
- A tuberculin skin test (TST) survey was conducted among children aged 3-60 months in Botswana during July-August 1996.
- TST reactivity was assessed, with induration >= 10 mm considered a positive result.
Main Results:
- The study found that most positive TST results (induration >= 10 mm) among children in Botswana were attributable to TB infection.
- The findings suggest that TST reactivity in this population is not primarily driven by previous BCG vaccination.
Conclusions:
- The tuberculin skin test (TST) remains a valuable diagnostic tool for pediatric tuberculosis (TB) in settings with high BCG vaccination rates.
- The TST can effectively differentiate between TB infection and BCG-induced reactivity in children in Botswana.
Abstract:
Tuberculosis (TB) causes more deaths worldwide than any other infectious disease: in 1995, TB caused an estimated 3 million deaths, of which 170,000 (6%) occurred among children aged <15 years (1,2). Diagnosing TB in children often is difficult and relies on clinical judgement and use of algorithms that include chest radiography and the tuberculin skin test (TST). However, interpretation of TST reactivity can be complicated by many factors other than infection with Mycobacterium tuberculosis. For example, previous Bacille Calmette-Guérin (BCG) vaccination or exposure to nontuberculous mycobacteria can result in positive TST reactions indistinguishable from those caused by M. tuberculosis (3). In contrast, such factors as human immunodeficiency virus (HIV) infection, poor nutritional status, and recent viral or bacterial infections or vaccination with live virus can reduce response to the TST (4). To assess the use of the TST for diagnosing pediatric TB in a population with high BCG coverage, a TST survey was conducted during July-August 1996 among children aged 3-60 months in Botswana (1991 population: 1.3 million). The findings indicate that most positive TSTs (induration > or =10 mm) among children in Botswana can be attributed to TB infection rather than previous BCG vaccination and that the TST remains useful for diagnosing pediatric TB in Botswana.