Tuberculin skin test survey in a pediatric population with high BCG vaccination coverage -- Botswana, 1996.

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.