Reprodutibilidade e validade de um questionário de frequência alimentar para população adulta de Porto Alegre e região metropolitana

Abstract

Reliable and accurate instruments for diet measurements are necessary to study the relationship between diet and health outcomes. The aim of this study was to assess the reproducibility and validity of a 120-item Food Frequency Questionnaire (FFQ) among adults living in the metropolitan region of Porto Alegre, Brazil. We applied two FFQ and three 24-hour dietary recalls (24h-R) to 128 individuals (20-69 years). Both reproducibility and validity were assessed by Bland-Altman method and Intraclass Correlation Coefficient (ICC). The validity was also assessed by cross-classification of quartiles of nutrients intake derived from the two methods and by weighted kappa. The nutrients were adjusted for total energy intake and the correlations were de-attenuated by the ratio of the intra- and inter-individual variances. The energy and nutrients intake was higher in the first FFQ (FFQ1) than in the second FFQ (FFQ2). The wideness of limits of agreement for means ratio between FFQ1 and FFQ2 were lowest for carbohydrate,