Tuberculosis casefinding by tuberculin testing among various age children with a discussion of some theoretical problems.

We have previously reported the results of ten years of systematic tuberculin Qsting of kindergarten and first grade children in Kansas City, Missouri. This report adds seven yeas of testing in different age groups (8th and 9th; and 4th and 5th grades). As reported in the previous study, the prevalence rates and conversion rates to tuberculin are markedly different depending on the frequency at which the children are retested. Yearly retesting appears to result in abnormally high conversion rates when the prevalence rates in that age group are considered. Retesting at seven and eight year intervals does not reveal this stimulating effect of retesting. Discussion of the stimulating effect of retesting with both tuberculin and histoplasmin is documented. Some of the practical implications are discussed. The efficacy of the tuberculin test as a case finding tool is again demonstrated although the frequency of finding new cases in only about 95 in the older children as was demonstrated in the younger children. The finding of 7 per 1,000 new active cases among 13,329 household and non-household contacts of positive reactors in children is still a considerable yield. Prevalence of infection in 10 and 11 year old children in Kansas City to skin tests with antigens of Mycobacterium batteii and M. kansasii is presented. The rates among Negro children were found to be at about twice those among white children for both of these antigens. Some of the theoretical aspects of infection rates and stimulation of tuberculin and histoplasmin reactions by retesting, are discussed.