Food allergy QoL questionnaire for children aged 0-12 years: content, construct, and cross-cultural validity

Background To date, there is no food allergy-specific questionnaire that allows parents to report children's health-related QoL (HRQL) from the child's perspective. Objective The aim of this study was to develop a sensitive, multi-dimensional measure to assess parental perception of HRQL in children aged 0-12 years with food allergy. Methods The Food Allergy QoL - Parent Form (FAQLQ-PF) was developed and validated in four stages: (1) item generation using focus groups, expert opinion, and literature review; (2) item reduction, using clinical impact and factor analysis; (3) internal and test-retest reliability and construct validity were evaluated using relevant scales of the Child Health Questionnaire (CHQ)-28 and the disease-specific food allergy independent measure (FAIM); and (4) cross-cultural and content validity was examined by administering the questionnaire in a US sample. Results Stage 1: Saturation was reached at 110 items. Stage 2: The reduced instrument has 14 items for children < 4 years and 26 and 30 items for children aged 4-6 years and 7-12 years, respectively. Factor analysis revealed three subscales: emotional impact, food anxiety, and social and dietary limitations, accounting for 68% of the variance. Stage 3: Cronbach's alpha > 0.7 for subscales and total score. Construct validity was demonstrated by significant correlations between relevant scales of the CHQ-28 and FAQLQ-PF subscales (r=0.69-0.77, P < 0.01), and between FAQLQ-PF subscales and the FAIM. Sensitivity was shown by significant within-group differences in a sample of 124 food-allergic children. Stage 4: The FAQLQ-PF was validated in a sample of US children, Cronbach's alpha > 0.7 for subscales and total score. Construct validity was demonstrated by significant correlations between FAQLQ-PF and the FAIM (parent report) and between the FAQLQ-PF and the FAIM (child report). No differences were observed between the US and Irish scores. Conclusion The FAQLQ-PF is psychometrically robust, with excellent reliability and validity.