Development and validation of the Food Expectation Questionnaire (FEX-Q) to assess food-related perceptions and symptom expectations

BackgroundFood-related gastrointestinal (GI) symptoms are highly prevalent in patients with IBS. Although dietary components may trigger symptoms through luminal mechanisms, cognitive expectations may also shape symptom perception within the gut-brain axis. No validated instrument currently exists to measure food-related symptom expectations. Hence, we developed and validated the Food Expectation Questionnaire (FEX-Q). MethodsThe FEX-Q was developed using a stepwise process including focus group interviews and face-to-face validation to ensure content validity. The finalized digital questionnaire presents 44 food images with six items rated on a visual analogue scale (VAS; 0-100), including the core item assessing food-related symptom expectation ("How severe GI symptoms do you expect after eating this food?"). Additional domains assess taste preference, willingness to eat, perceived healthiness, and perceived fat and carbohydrate content. The finalized FEX-Q was administered in a nationwide online validation survey of adults with IBS and non-IBS controls in Sweden. Participants also completed validated questionnaires including GI symptom severity (combined GSRS), psychological distress (HADS), food-related quality of life (FR-QOL), and a screening tool for food avoidance (NIAS). ResultsTwenty adults with IBS and non-IBS controls participated in the face-to-face validation, resulting in a final version of the FEX-Q comprising 44 food images, which were properly identified and provided a range of macronutrient distributions and trigger foods. In the nationwide online study including 134 patients with IBS and 126 non-IBS controls, the FEX-Q demonstrated strong known-groups validity (mean symptom expectation 18.4 in controls vs 50.1 in IBS), strong construct validity (perceived vs actual fat content r=0.78, p<0.001 and carbohydrate content r=0.59, p<0.001), significant convergent validity with GI symptom severity and food-related quality of life, and high internal consistency (split-half reliability Spearman-Brown corrected r=0.88). ConclusionThe FEX-Q can capture individual food-related symptom expectations to distinct food images. This reliable measurement can be useful to reveal the mechanism of food-related symptom expectations and provide clinically relevant insights for personalized dietary management