Background and Objectives: There is no food frequency questionnaire by which gluten consumption in patients with ulcerative colitis could be evaluated in Iran. The aim of this study was to assess the validity and reliability of a food frequency questionnaire to measure gluten consumption in ulcerative colitis. After designing the questionnaire, its validity and reliability were measured to be used in studies in this area.

Materials and Methods: The method used to assess validity was panel of experts. The designed questionnaires were sent to 10 experts in nutrition to get their opinion to the questions related to CVR and CVI. To evaluate the reliability, 3 questionnaires with one-month intervals were filled by the experts, and Cronbach's alpha coefficient was calculated. To ensure the ability to use it in the patients, the questionnaire's reliability were also assessed among a group of patients with ulcerative colitis.

Results: CVR coefficient calculated for the necessity of the questions was 0.695. CVI was calculated to measure the relevance of the questions to the objectives, and the content of 0.923 was obtained. Cronbach's alpha that measured in the panel of experts and among the patients was 0.761 and 0.786, respectively in the pilot study.

Conclusion: The present study showed that food frequency questionnaire designed to measure the consumption of gluten has good reliability and validity, and can be used particularly in patients with ulcerative colitis.

Keywords: Food frequency questionnaire, Ulcerative colitis, Gluten, Validity, Reliability authors