Reproducibility and relative validity of the EatWellQ8 web-based food frequency questionnaire against a paper-based food frequency questionnaire and a 4-day weighed food record

Abstract

Background:The web-based EatWellQ8 food frequency questionnaire (FFQ) was developed as a dietary assessment tool for healthy adults in Kuwait. Validation against reliable instruments and an assessment of its reproducibility are required to ensure its accuracy in computing nutrient intake Objective:To assess the reproducibility and validity of the EatWellQ8 FFQ against a paper based (PFFQ) and a 4-day weighed food record (WFR). Methods:Reproducibility of the EatWellQ8 FFQ was assessed using test-retest methodology. Participants were required to complete the FFQ at two time points, 4 weeks apart. To assess validity of the EatWellQ8 FFQ, a subset of the participants were asked to complete a PFFQ or a 4-day WFR 1 week after administration of the EatWellQ8 FFQ. The level of agreement between nutrient and food group intakes estimated by repeated EatWellQ8 FFQ and the EatWellQ8 FFQ and the PFFQ and the 4-day WFR were evaluated using Bland-Altman methodology and classification into quartiles of daily intake. Crude unadjusted correlation coefficients were also calculated. Results:A total of 99 participants (65% female: 35% male) completed the study, 53 participated in the reproducibility study and the 4-day WFR validity study (mean age 37 years) and a further 46 participated in the PFFQ validity study (mean age 36 years). Crude unadjusted correlations for repeated EatWellQ8 FFQ ranged from (0.37-0.82) (P<0.01). Mean cross-classification into “exact agreement plus adjacent” was 88% for nutrient intakes, 86% for food groups, and Bland-Altman plots showed good agreement for energy-adjusted macronutrient intakes. Agreement between the EatWellQ8 FFQ and PFFQ varied, with crude unadjusted correlations ranging from (0.42-0.73) (P<0.05). Mean cross-classification into “exact agreement plus adjacent” was 84% for nutrient intake and 74% for food groups. Bland-Altman plots showed moderate agreement for both energy and energy-controlled nutrient intakes. Crude unadjusted correlations for the EatWellQ8 FFQ and the 4-day WFR ranged from (0.40-0.88) (P<0.01). Mean cross-classification into “exact agreement plus adjacent” was 85% for nutrient intake and 83% for food groups. Bland-Altman plots showed moderate agreement for energy-adjusted macronutrient intakes. Conclusions:Results indicate that the web-based EatWellQ8 FFQ is reproducible for assessing nutrient and food group intake and has moderate agreement compared to a PFFQ and a 4-day WFR for measuring energy and nutrient intakes.