Evaluation of a modified Italian European Prospective Investigation into Cancer and Nutrition food frequency questionnaire for individuals with celiac disease

Background To date, it is unclear whether individuals with celiac disease following a gluten-free (GF) diet for several years have adequate intake of all recommended nutrients. Lack of a food frequency questionnaire (FFQ) for individuals with celiac disease could be partly responsible for this still-debated issue. Objective The aim of the study is to evaluate the performance of a modified European Prospective Investigation into Cancer and Nutrition (EPIC) FFQ in estimating nutrient and food intake in a celiac population. Design In a cross-sectional study, the dietary habits of individuals with celiac disease were reported using a modified Italian EPIC FFQ and were compared to a 7-day weighed food record as a reference method. Participants/setting A total of 200 individuals with histologically confirmed celiac disease were enrolled in the study between October 2012 and August 2014 at the Center for Prevention and Diagnosis of Celiac Disease (Milan, Italy). Main outcome measures Nutrient and food category intake were calculated by 7-day weighed food record using an Italian food database integrated with the nutrient composition of 60 GF foods and the modified EPIC FFQ, in which 24 foods were substituted with GF foods comparable for energy and carbohydrate content. Statistical analyses performed An evaluation of the modified FFQ compared to 7-day weighed food record in assessing the reported intake of nutrient and food groups was conducted using Spearman’s correlation coefficients and weighted k. Results One hundred individuals completed the study. The Spearman’s correlation coefficients of FFQ and 7-day weighed food record ranged from .13 to .73 for nutrients and from .23 to .75 for food groups. A moderate agreement, which was defined as a weighted k value of .40 to .60, was obtained for 30% of the analyzed nutrients, and 40% of the nutrients showed values between .30 and .40. The weighted k exceeded .40 for 60% of the 15 analyzed food groups. Conclusions The modified EPIC FFQ demonstrated moderate congruence with a weighed food record in ranking individuals by dietary intakes, particularly food groups.