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.