An evaluation of the numerical criterion for "positive" with skin tests using Mycobacterium leprae antigens

There has been disagreement regarding the reaction sizes which could demarcate "positive" and "negative" reactions with Mycobacterium leprae antigens. In this investigation, positives and negatives were differentiated using statistical methods. The results of this analysis were in agreement with the commonly used reaction size of 3mm and larger being "positive" for Mitsuda reactivity. With Fernandez reactivity there is disagreement with the earlier recommended l0mm reaction size, the conclusion of this study being 3mm or more be considered positive. With reactivity to Soluble Protein Antigen, there is no earlier data and it is suggested that reactions of 3mm or less be considered "negative" and 9mm or more "positive".