Abstract
IntroductionBiomarkers are a good choice to be used in the validation of food frequency questionnaire due to the independence of their random errors.ObjectiveTo assess the validity of the potassium and sodium intake estimated using the Food Frequency Questionnaire ELSA-Brasil.Subjects/MethodsA subsample of participants in the ELSA-Brasil cohort was included in this study in 2009. Sodium and potassium intake were estimated using three methods: Semi-quantitative food frequency questionnaire, 12-hour nocturnal urinary excretion and three 24-hour food records. Correlation coefficients were calculated between the methods, and the validity coefficient was calculated using the method of triads. The 95% confidence intervals for the validity coefficient were estimated using bootstrap sampling. Exact and adjacent agreement and disagreement of the estimated sodium and potassium intake quintiles were compared among three methods.ResultsThe sample consisted of 246 participants, aged 53±8 years, 52% of women. Validity coefficient for sodium were considered weak (рfood frequency questionnaire actual intake = 0.37 and рbiomarker actual intake = 0.21) and moderate (рfood records actual intake 0.56). The validity coefficient were higher for potassium (рfood frequency questionnaire actual intake = 0.60; рbiomarker actual intake = 0.42; рfood records actual intake = 0.79). Conclusions: The Food Frequency Questionnaire ELSA-Brasil showed good validity in estimating potassium intake in epidemiological studies. For sodium validity was weak, likely due to the non-quantification of the added salt to prepared food.
Highlights
Biomarkers are a good choice to be used in the validation of food frequency questionnaire due to the independence of their random errors
The validity coefficient were higher for potassium
One limitation of the use of biomarkers is reference time, as they reflect nutrient intake in the short term, i.e., intake at a point in time [4]. In light of this limitation, Kaaks [7] recommends using the triangulation technique or method of triads, as this method allows the comparison of food intake estimated by Food Frequency Questionnaire (FFQ), Food Records (FRs) and biomarker with actual intake (AI) through the use of the validity coefficient
Summary
To assess the validity of the potassium and sodium intake estimated using the Food Frequency Questionnaire ELSA-Brasil. A subsample of participants in the ELSA-Brasil cohort was included in this study in 2009. Sodium and potassium intake were estimated using three methods: Semi-quantitative food frequency questionnaire, 12-hour nocturnal urinary excretion and three 24-hour food records. Correlation coefficients were calculated between the methods, and the validity coefficient was calculated using the method of triads. The 95% confidence intervals for the validity coefficient were estimated using bootstrap sampling. Exact and adjacent agreement and disagreement of the estimated sodium and potassium intake quintiles were compared among three methods
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