Atopy Patch Test in the Diagnosis of Food Allergens in Infants with Allergic Proctocolitis Compared with Elimination/Introduction Challenge

Allergic proctocolitis is a cell-dependent food allergy that is present in both breast and formula-fed infants. The presence of blood with different amounts in the stool is the main manifestation of the disease. Different results have been published on the accuracy and specificity of the atopic patch test (APT). The purpose of this study was to evaluate the results of the APT and compare them with those obtained in the food elimination/introduction (E/I) challenge, as the gold standard of confirming the allergy. Twenty-eight patients (18 boys, 10 girls, <1 year) with allergic proctocolitis were recruited in this study. The mean age of the disease onset and enrolling the study were 2.23 +/- 1.7 and 5.25 +/- 2.19 months, respectively. After performing APT with fresh foods, an E/I challenge was done in a patient with positive tests, and results were analyzed. APT was positive in 14/28 (50%) individuals. The most common foods detected by APT in all of the individuals were: milk (10/28), rice (5/28), soy (4/28), and egg white (4/28), while in E/I challenge in the APT-positive individuals were: milk (8/10), rice (3/5), egg white (1/4), and soy (0/4). APT was positive in half of the infants<1 year with allergic proctocolitis and there was no significant correlation between the APT results and the E/I challenge test for all foods. Comparing the results of APT and E/I challenge methods showed a convergence between the milk and rice sensitivity, thus we suppose APT to be a useful tool in identifying these two allergens in cell-mediated food allergies like allergic proctocolitis.