Dietary Assessment in the MetaCardis Study: Development and Relative Validity of an Online Food Frequency Questionnaire.

Background: The European study MetaCardis aims to investigate the role of the gut microbiota in health and cardiometabolic diseases in France, Germany, and Denmark. To evaluate long-term diet-disease relationships, a food frequency questionnaire (FFQ) was found to be the most relevant dietary assessment method for the MetaCardis study.

Objective: The objectives of this study were to describe the development of three semiquantitative online FFQs used in the MetaCardis study-one FFQ per country-and to assess the relative validity of the French MetaCardis FFQ.

Design: The layout and format of the MetaCardis FFQ was based on the European Prospective Investigation of Cancer (EPIC)-Norfolk FFQ and the content was based on relevant European FFQs. Portion size and nutrient composition were derived from national food consumption surveys and food composition databases. To assess the validity of the French MetaCardis FFQ, a cross-sectional study design was utilized.

Participants/setting: The validation study included 324 adults recruited between September 2013 and June 2015 from different hospitals in Paris, France.

Main Outcome Measures: Food intakes were measured with both the French MetaCardis FFQ and 3 consecutive self-administered web-based 24-hour dietary recalls (DRs).

Statistical Analyses Performed: Several measures of validity of the French MetaCardis FFQ were evaluated: estimations of food groups, energy, and nutrient intakes from the DRs and the FFQ, Spearman and Pearson correlations, cross-classification, and Bland-Altman analyses.

Results: The French MetaCardis FFQ tended to report higher food, energy, and nutrient intakes compared with the DRs. Mean correlation coefficient was 0.429 for food, 0.460 for energy, 0.544 for macronutrients, 0.640 for alcohol, and 0.503 for micronutrient intakes. Almost half of participants (44.4%) were correctly classified within tertiles of consumption, whereas 12.9% were misclassified in the opposite tertile. Performance of the FFQ was relatively similar after stratification by sex.

Conclusions: The French MetaCardis FFQ was found to have an acceptable level of validity and may be a useful instrument to rank individuals based on their food and nutrient intakes.