EVALUATION OF VARIABLES INFLUENCING THE OUTCOME OF THE ATOPY PATCH TEST

Background: The number of positive atopy patch test (APT) results in p atients with atopic eczema (AE) varies in different studies, probably because of different test techniques. Variables that may influence the outcome of the APT were evaluated. Methods: APTs were performed in 84 patients with AE, 30 control patients with atopic disease, and 85 hea lthy volunteers, with house dust mite and grass pollen allergens in co ncentrations of 100, 1000, 10,000 and 100,000 allergenic units/ml. The influence of 0, 10 or 20 tape strippings was investigated. The tests were performed on the back and/or the antecubital fossa and evaluated after 20 minutes and 24, 48, and 72 hours. In all patients the total a nd specific serum IgE levels were measured. Results: The maximal numbe r of positive APT results were obtained under the following conditions : an allergen concentration equal to 10,000 allergenic units/ml, 10 ta pe strippings and readings at 24 and 48 hours. Positive APT results we re observed in five of 30 control patients with atopic disease and in none of 85 healthy volunteers. Statistically significantly higher tota l and allergen-specific serum IgE levels were found in the group of pa tients with AE with positive APT results. Conclusions: We recommend th e previously described conditions to get an optimal method for APT. Th e correlation between the APT and the total and specific serum IgE sug gests an important role for IgE in the reaction mechanism behind the A PT.