Patterns of tuberculin hypersensitivity in South Africa.
The frequency distribution patterns displayed by delayed hypersensitivity responses to 170 000 low-dose RT 23 Mantoux tests, measured as induration sizes, were determined for the South African population under 19 years of age. There were wide differences between the results obtained in different age groups and also between those obtained in different geographical regions. Nonspecific hypersensitivity to the tuberculin test, probably arising from nontuberculous mycobacterial infections and particularly BCG vaccinations, is generally high, hampering the calculation by commonly used methods of the sizes of reactor components. In South Africa a high degree of specificity of the tuberculin test may nevertheless be found in children aged 5-9 years who have no BCG scars.