Development and validation of a quantitative food frequency questionnaire to assess free sugar intake among Sri Lankan preschool children

The present study aims to develop a quantitative food frequency questionnaire (FFQ) to assess free sugar intake as a whole and at the food group levels, retrospectively, over the past 3 months among 4 to 5-year-old preschool children in the Colombo district, Sri Lanka. Then, to assess its reliability and relative validity. In the development phase, three 24-hour dietary recalls (24 hDRs) of 518 preschool children were collected from caregivers. Based on that, a 67-item FFQ was developed, including commonly consumed free sugar-containing food items. The validation study was conducted among another 108 preschool children. The relative validity of the FFQ was assessed by comparing it with the 24 hDRs. The test–retest reliability was assessed by repeated application of the FFQ to the same population after 6 weeks. Wilcoxon sign rank test, cross-classification with weighted Kappa statistic, Spearman rank correlation and Bland–Altman plots were used for comparison. Comparing the free sugar intake calculated by the two methods showed no difference (P = 0⋅13), a good correlation (0⋅89), good agreement in cross-classifying participants (78⋅4 % correctly classified) and a good agreement in Bland–Altman plots. Repeated application of the FFQ yielded; no differences in free sugar intake values (P = 0⋅45) a good correlation (0⋅71), acceptable agreement in cross-classifying participants (52⋅3 % correctly classified) and acceptable agreement in the Bland–Altman plot. Results were the same for all food groups. According to the results, the newly developed quantitative FFQ provides a relatively valid and reliable measure for quantifying free sugar intake among preschool children as a whole or by food group.