Methods
Our IQ-OFA study enrolled children aged less than 13 years with food allergy who had undergone OFC at National Hospital Organization Mie National Hospital, a tertiary hospital for pediatric allergies. In our current study, we focused on children younger than 72 months of age who had egg allergy, since that is the most prevalent pediatric food allergy in Japan15 and most resolve by 72 months.16
OFCs were performed based on the Japanese Guideline for Food Allergy.15 The total challenge dose was decided for each child patient by pediatric allergy specialists based on the patient’s history of food–induced reactions, sIgE level and other related factors. The low dose was at 1/32 of a cooked whole egg, the medium dose 1/8–1/2 of a cooked egg, and the high dose one cooked whole egg. Then a registered dietitian provided dietary advice for minimal avoidance of egg based on the OFC results. When the OFC was negative, a caregiver was advised to give the child egg at home in an amount not exceeding the total challenge dose. When the OFC was positive but the induced symptoms were mild, the advice was to consume egg in an amount not exceeding the threshold dose at home. When the OFC was positive, with moderate to severe induced symptoms, complete elimination of egg was advised.15
The amount of egg consumed at home was classified into 5 levels: level 0, complete elimination; level 1: cooked egg yolk without egg white (1/32 egg equivalent); level 2: a small roll or stick of bread (1/16–1/8 egg equivalent); level 3: a small donut or small cake (1/4–1/2 egg equivalent); level 4: 1/2–1 cooked egg; and level 5: >1 cooked egg. At 1 year after OFC, the amount of egg that each patient safely consumed in daily life was surveyed using a web–based questionnaire or by interview at an outpatient clinic and classified into the 6 levels described above. We classified the patient as “Outgrowing” (Group O) if the level was higher than the initial level, or as “Non-outgrowing” (Group N) if the level remained the same or had decreased.
The QoL of children was evaluated using the Japanese version19 of the Food Allergy QoL Questionnaire–Parent Form (FAQLQ–PF).20 The FAQLQ–PF allows parents to report children’s health-related QoL from the child’s perspective. It consists of 3 domains: emotional impact (EI), food anxiety (FA) and social dietary limitations (SDL). The parents/caregivers of the patients answered each question on a 7–point Likert scale from “not at all” to “extremely”, in which a higher score indicates a worse QoL. The FAQLQ–PF was administered at OFC (baseline) and after 1 year.