Reproducility of APT

Background: The aim of the present study was to evaluate the reproducibility of Atopy Patch Tests (APT) by simultaneously applying 2 identical patch test series in 85 patients affected by atopic dermatitis. Methods: The test substances included 2 commercially available materials (Dermatophagoides mix 20% pet., Alternaria Alternata 2.4% pet.) and 8 self-made food preparations containing egg yolk, egg white, peanuts, cow’s milk, soy milk, wheat flour, rice, and corn meal. Results: The percentage of agreement in the frequency of positive responses varied from 87.1% (corn meal) to 100% (soy milk). The reproducibility was satisfactory for Dermatophagoides mix, Alternaria alternata, egg yolk, and soy milk. Conclusions: For Dermatophagoides and Alternaria Alternata the agreement rate was similar to that of standard patch tests and therefore APTs may be considered sufficiently reproducible to be employed as a diagnostic testing procedure. As regards food materials, such as soy milk, egg yolk, and corn meal, APT reproducibility may be acceptable. For other foodstuffs, preparation methods have to be improved.