Development and preliminary validation of the food intolerance Quality of Life Questionnaire (FIQLQ): Adult Form

Background Approximately 20% of children and adults avoid certain foods because of perceived food intolerance. Valid and reliable health-related quality of life instruments are needed to measure changes following clinical, therapeutic or policy interventions. However, there are no disease-specific quality of life instruments for adults with food intolerances. Objective To develop the Food Intolerance Quality of Life Questionnaire FIQLQ. Then to conduct psychometric validation including reliability and construct validity. Methods We adapted the existing Food Allergy Quality of Life questionnaire (FAQLQ) for interviews with 14 adults with food intolerance. For preliminary psychometric validation, 229 adults with food intolerances completed the online electronic version of FIQLQ. Results The resultant FIQLQ had 18 items which loaded onto 3 subscales—Emotional Impact, Social and Dietary Restrictions, Reactions and Avoidance. Each subscale had excellent internal consistency reliability (Cronbach’s α 0.81–0.94). Content, convergent and construct validity was supported by significant correlations of FIQLQ subscale scores with hypothesised variables including age, numbers of symptoms and level of stress experienced due to intolerance. Conclusion The FIQLQ has good reliability, construct validity and internal consistency. It is short and easy to use, providing a good tool for evaluating quality of life in the clinical research setting and to inform health and regulatory policies.