Relative Validity Of A Computer-Based Semi-Quantitative Ffq For Use In The Pelotas (Brazil) Birth Cohort Studies

Objective:To assess the relative validity of a FFQ developed for the Pelotas Birth Cohort Studies.Design:Participants completed a ninety-two-food-item FFQ and then answered two 24-h recalls (24HR), one in-person interview and a second one by telephone, administered 14-28 d apart. Median and relative differences of energy, fifteen nutrients and eleven food groups were estimated based on the FFQ and the average of two 24HR. Nutrients were log-transformed and energy-adjusted using residual method. Validity was assessed by crude, energy-adjusted and de-attenuated Pearson and Lin's concordance correlation coefficients. Agreement of quartiles and weighted kappa were performed. Differences in energy and nutrient estimations between methods were plotted in Bland-Altman graphs.Setting:Pelotas, southern Brazil.Participants:Two hundred fifty-four participants randomly selected from the 1993 Pelotas Birth Cohort during the 22-year follow-up (2015).Results:The FFQ overestimated energy and most nutrients and food groups compared with the two 24HR. Energy-adjusted and de-attenuated Pearson correlation coefficients ranged from 0 center dot 21 to 0 center dot 66. The highest energy-adjusted and de-attenuated concordance correlation coefficients were observed for Ca (0 center dot 48), niacin (0 center dot 32), Na (0 center dot 29), vitamin C (0 center dot 28) and riboflavin (0 center dot 25). The percentage of nutrients classified into the same and opposite quartiles ranged from 36 center dot 5 to 60 center dot 3 %, and from 4 center dot 8 to 19 center dot 1 %, respectively. Weighted kappa was moderate for Ca (0 center dot 51), beans and legumes (0 center dot 50) and milk and dairies (0 center dot 49).Conclusions:The FFQ provides a reasonable dietary intake assessment for habitual food consumption. However, the relative validity was weak for specific nutrients and food groups.