Dose response study of atopy patch test in children with atopic eczema

Eczematous reactions in atopic eczema (AE) patients can be elicited by epicutaneous application (patch testing) of IgE-inducing allergens (atopy patch test [APT]). The feasibility and technical aspects of this method in children were investigated in a multicenter trial in seven German university departments. Thirty children with AE (age range, 5-14 years; mean age, 9.4 years) were tested with lyophilized allergen preparations of house dust mite (Dermatophagoides pteronyssinus), cat dander, and grass pollen in petrolatum on uninvolved, untreated, and unabraded back skin. Allergens were applied in concentrations of 300, 1000, 3000, and 5000 protein nitrogen units per gram (PNU/g). Reactions were evaluated after 48 and 72 hours according to ICDRG guidelines and compared with the patients' allergen-specific histories of eczema flares. A total of 41% of children reacted with at least one clearcut positive APT reaction to D. pteronyssinus, 17% reacted to cat dander, and 15% reacted to grass pollen. The frequency of positive reactions increased with allergen concentrations. For D. pteronyssinus and grass pollen, the reactivity was nearly similar, with 3000 and 5000 PNU/g, respectively, whereas with cat dander, a higher frequency of positive APT reactions was obtained with 5000 PNU/g. Positive skin prick tests (and specific IgE) were seen in 67% (40%) of patients to D. pteronyssinus, in 43% (43%) to cat dander, and in 57% (57%) to grass pollen. The concordance of APT results with history was 56% for D. pteronyssinus, 61% for cat dander, and 78% for grass pollen. No severe side effects were seen. These data may contribute to the concurrent standardization of the APT as a clinical routine diagnostic instrument in AE. In children, clear-cut positive APT reactions can be elicited with comparatively low allergen concentrations on unabraded skin. Significant clinical relevance as determined by a dear-cut patient history was highest for grass pollen as a seasonal aeroallergen. Larger dose-response studies are necessary to determine statistically based optimal test concentrations for different age groups. The relevance of aeroallergens for inducing flares in children with AE may be evaluated by APT.