The HealthNuts population-based study of paediatric food allergy: validity, safety and acceptability

Background The incidence of hospital admissions for food allergy-related anaphylaxis in Australia has increased, in line with world-wide trends. However, a valid measure of food allergy prevalence and risk factor data from a population-based study is still lacking. Objective To describe the study design and methods used to recruit infants from a population for skin prick testing and oral food challenges, and the use of preliminary data to investigate the extent to which the study sample is representative of the target population. Methods The study sampling frame design comprises 12-month-old infants presenting for routine scheduled vaccination at immunization clinics in Melbourne, Australia. We compared demographic features of participating families to population summary statistics from the Victorian Perinatal census database, and administered a survey to those non-responders who chose not to participate in the study. Results Study design proved acceptable to the community with good uptake (response rate 73.4%), with 2171 participants recruited. Demographic information on the study population mirrored the Victorian population with most the population parameters measured falling within our confidence intervals (CI). Use of a non-responder questionnaire revealed that a higher proportion of infants who declined to participate (non-responders) were already eating and tolerating peanuts, than those agreeing to participate (54.4%; 95% CI 50.8, 58.0 vs. 27.4%; 95% CI 25.5, 29.3 among participants). Conclusion A high proportion of individuals approached in a community setting participated in a food allergy study. The study population differed from the eligible sample in relation to family history of allergy and prior consumption and peanut tolerance, providing some insights into the internal validity of the sample. The study exhibited external validity on general demographics to all births in Victoria.