Sensitivity to sensitins and tuberculin in Swedish children. Part 5: A study of school children in an inland rural area.

SETTING: Since 1986 we have tested approximately 7000 non-BCG-vaccinated Swedish children with tuberculin and with Mycobacterium avium or M. scrofulaceum sensitin. In Göteborg, an urban coastal area, 25% of 8-9-year-old school children reacted to M. avium sensitin and 32% of M. scrofulaceum sensitin using a 6 mm cut-off. OBJECTIVE: To evaluate if geographical factors have an influence on the prevalence of children reacting to tuberculin and sensitins. DESIGN: 2000 schoolchildren of the same age as those in Göteborg but living in an inland rural area were Mantoux-tested in a similar way (simultaneously on separate arms with PPD RT23 and either of the two sensitins). RESULTS: 15% reacted to PPD RT23, 9.7% to M. avium and 13.9% to M. scrofulaceum sensitin. None of the children with a PPD RT23 reaction > = 6 mm showed signs of tuberculosis or had any known exposure. A reaction to PPD RT23 was usually combined with a still larger sensitin reaction. CONCLUSION: There was a considerable geographic difference in sensitin reactivity, low in an inland rural area compared to a coastal urban area. Children reacting to PPD RT23 had probably not been infected by M. tuberculosis but more likely by atypical mycobacteria. The reactions should be interpreted as cross-reactions.