Atopy patch test (APT) in the diagnosis of food allergy in children with atopic dermatitis

Abstract

BACKGROUND: Atopic Dermatitis is a chronic inflammatory skin disease. Food allergens are important in the pathogenesis in 1/3 of the cases. Several mechanisms are involved in the pathogenesis of Atopic Dermatitis. Immediate reactions are identified by both measurement of specific IgE and skin prick test. Atopy Patch Test seems to be relevant in the investigation of patients with suspected delayed-type reactions. OBJECTIVES: To evaluate the standardization of this method concerning allergen concentration, occlusion time and interpretation, and determine the specificity and sensitivity of the Atopy Patch Test according to the skin prick test and specific IgE levels in food allergy diagnosis in children with Atopic Dermatitis. METHODS: Seventy-two children, aged 2-12 years were selected and followed at the allergy clinic of the Hospital São Zacharias. Skin prick test, specific IgE and food Atopy Patch Test (cow's milk, egg, soy and wheat) were carried out. Three groups were submitted to the Atopy Patch Test: (1) Atopic Dermatitis with or without Rhinitis and Asthma; (2) Rhinitis and or Asthma without AD; (3) Healthy individuals. RESULTS: In group 1, 40% of the patients presented positive reactions. The longer the exposure time (48h and 72h), the higher the sensitivity. In group 2, the test was more specific than sensitive for all the extracts, with increased sensitivity the longer the time of exposure (72h). In group 3, 8.3% presented positive tests. CONCLUSION: APT evidenced a great diagnostic value in late-phase reactions to food, with high specificity. It showed to be a specific and reliable tool in comparison with the healthy group's results.