The diagnostic value of atopy patch test (APT) with regard to late-phase clinical reactions to food in children with atopic dermatitis (AD)

Abstract

Rationale Non IgE-mediated adverse responses to food tent to involve a T-cell mediated delayed hypersensitivity reaction that can be evaluated by the APT. The aim was to evaluate the diagnostic value of the APT with regard to late-phase reactions observed in double blind, placebo-controlled food challenges (DBPCFCs) with cow's milk, hen's egg, wheat, in children with AD. Methods One hundred and thirteen children [69 males, median age 4.2 years (range 4 months-12.7 years)] suffering from AD and suspected food-related clinical symptoms were investigated with APT and DBPCFCs. Results We found that late-phase clinical reactions to food observed in DBPCFCs were associated with a positive APT; the sensitivity to cow's milk was 64%, to hen's egg 86%, to wheat 100%; the specificity was 86% for milk, 73% for egg and 95% for wheat; positive predictive value was 47% for milk, 22% for egg, 40% for wheat; negative predictive values were 93%, 98% and 100% respectively. Of 229 DBPCFCs, 24 (40%) were assessed as positive for cow's milk, 32 (53%) for hen's egg, 4 (7%) for wheat. Out of 42 patients with APT positive reactions, 20 (53.8%) had positive response to hen's egg, 4 (10.8%) to milk, 4 (10.8%) to wheat, 12 (32.3%) to milk and egg, 2 (5.4%) to milk and wheat. Conclusions Our findings confirm that the APT may be a valuable additional tool in the diagnostic work-up of food allergy in children with AD because of its high specificity and sensibility for late-phase clinical reactions; however DBPCFC must be still considered the diagnostic gold standard test.