Longitudinal validity and responsiveness of the Food Allergy Quality of Life Questionnaire – Parent Form in children 0–12 years following positive and negative food challenges

Summary Background There are no published studies of longitudinal health‐related quality of life (HRQL) assessments of food‐allergic children using a disease‐specific measure. Objective This study assessed the longitudinal measurement properties of the Food Allergy Quality of Life Questionnaire – Parent Form (FAQLQ‐PF) in a sample of children undergoing food challenge. Methods Parents of children 0–12 years completed the FAQLQ‐PF and the Food Allergy Independent Measure (FAIM) pre‐challenge and at 2 and 6 months post food challenge. In order to evaluate longitudinal validity, differences between Group A (positive challenge) and Group B (negative challenge) were expected over time. We computed correlation coefficients between change scores in the FAQLQ‐PF and change scores in the FAIM. To determine the minimally important difference (MID), we used distributional criterion and effect size approaches. A logistic regression model profiled those children falling below this point. Results Eighty‐two children underwent a challenge (42 positive; 40 negative). Domains and total score improved significantly at pos‐challenge time‐points for both groups (all P <0.05). Sensitivity was demonstrated by significant differences between positive and negative groups at 6 months [ F (2, 59)=6.221, P <0.003] and by differing improvement on relevant subscales ( P <0.05). MID was 0.45 on a seven‐point response scale. Poorer quality of life at baseline increased the odds by over 2.0 of no improvement in HRQL scores 6‐month time‐point. General maternal health (OR 1.252), number of foods avoided (OR 1.369) and children >9 years (OR 1.173) were also predictors. The model correctly identified 84% of cases below MID. Conclusion The FAQLQ‐PF is sensitive to change, and has excellent longitudinal reliability and validity in a food‐allergic patient population. The standard error of measurement value of 0.5 points as a threshold for meaningful change in HRQL questionnaires was confirmed. The FAQLQ‐PF may be used to identify problems in children, to assess the effectiveness of clinical trials or interventions, and to guide the development of regulatory policies. Cite this as : A. DunnGalvin, C. Cullinane, D. A. Daly, B. M. J. Flokstra‐de Blok, A. E. J. Dubois and J. O'B. Hourihane, Clinical & Experimental Allergy , 2010 (40) 476–485.