FFQ for the adult population of the capital of Ecuador (FFQ-Quito): development, reliability and validity

Objective To assess the reliability and validity of a semi-quantitative FFQ designed to evaluate the usual nutrient intake of adults in Quito, Ecuador. Design Dietary data using 24 h recalls (24hR) were used to design a list of commonly consumed foods. The relative validity of a 111-item FFQ was evaluated by comparing nutrient intakes against three non-consecutive 24hR. All nutrients were energy-adjusted. Reliability was assessed using two FFQ (FFQ1 and FFQ2) and assessed by the intra-class correlation coefficient. The comparisons between the FFQ and the 24hR were assessed by the de-attenuated Pearson correlation coefficient, weighted kappa and by Bland–Altman plots. Setting Quito, Ecuador. Subjects Overall, 345 adults were enrolled in the present study. Two hundred and fifty participated in FFQ development and ninety-five participated in the FFQ validity and reliability. Results The FFQ produced higher energy and nutrient intakes. Reliability correlation coefficients after adjusting for energy ranged from 0·62 to 0·88 for protein and Ca, respectively. For the validity study, energy-adjusted and de-attenuated correlation coefficients between the questionnaire and the 24hR ranged from 0·21 for fat to 0·65 for Ca. Only 4 % of the participants were grossly misclassified and 46 % had weighted kappa higher than 0·42. The Bland–Altman plot showed a constant bias with a tendency to increase according to the intake level. Conclusions The FFQ showed reasonably good relative validity and reliable measurements, especially for nutrients considered protective and risk markers of non-communicable disease, and can be used to assess usual nutrient intake in this population.