THE DIAGNOSTIC VALUE OF ATOPY PATCH TEST AND SKIN PRICK TEST IN CHILDREN WITH ATOPIC DERMATITIS AND SUSPECTED FOOD ALLERGY

Aim. To compare Atopy Patch Test (APT) and Skin Prick Test (SPT) to double blind placebo-controlled food challenges (DBPCFCs) for late-phase reactions to milk, egg and wheat in children with atopic dermatitis (AD). Methods. All the 131 consecutive children [(80 M (61%); median age: 44 months (range 4–151 months)] with AD, suspected of late-phase foodrelated clinical symptoms were investigated with SPT, APT and DBPCFCs. Results. Overall, we performed 512 DBPCFCs (256 with food: 85 milk, 100 egg, 71 wheat) and 77 (15%; all with food) were positive [33 for cow’s milk (38%; 17 late); 40 for egg (40%; 13 late) and 4 for wheat (6%; 3 late)]. APT resulted positive for milk in 23 children (18.6%), for egg in 42 (33.6%) and for wheat in 7 (5.5%) whereas SPT was positive for milk in 26 children (19.8%), for egg in 68 (51.9%) and for wheat in 6 (4.6%). The SS, SP, PPV and NPV of SPT and APT in assessing a late phase reaction to food are shown in the table. Milk Egg Wheat SPT APT SPT APT SPT APT SS 39% 53% 58% 81% 0 100 SP 74% 80% 48% 71% 96% 94% PPV 29% 41% 13% 27% 0 33% NPV 82% 87% 89% 96% 96% 100% Logistic regression showed that SPT and APT were significantly associated with a late phase reaction to milk (OR = 3.7; 95% CI: 1–12 andOR= 4.4; 95% CI: 1–14, respectively) and both positive tests quadruplicate the risk of a positive challenge. However, only APT was predictive for late phase reactions to egg (OR = 11; 95% CI: 2–60) and wheat (OR = 5.4; 95% CI: 1–8). Summary. 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 especially for egg and wheat, but it cannot replace DBPCFC. Conclusion. APT identifies children not at risk for late phase reactions to food; however, DBPCFC must still be considered as the diagnostic gold standard test.