title: Assessing the validity of a food frequency questionnaire among low-income women in São Paulo, southeastern Brazil.
abstract: This study describes the validity of a food frequency questionnaire (FFQ) in 93 low-income women (20-65 years), participating in a case-control study in São Paulo, Brazil. Two FFQ (FFQ1 and FFQ2, 12 months apart) and three 24-hour dietary recalls (24hR) were conducted between 2003 and 2004 to estimate dietary intake during the past year. The Pearson correlation coefficients (crude, energy-adjusted and de-attenuated) were used for comparisons between FFQ and 24hR. The agreement between the methods was further examined by the Bland-Altman analysis. For the assessment of long-term reliability, the energy-adjusted intra-class correlation coefficients were mostly around 0.40, but higher for vitamin A and folate (0.50-0.56). Energy-adjusted, attenuation-corrected Pearson validity correlations between FFQ and DR ranged from 0.30-0.54 for macronutrients to 0.20-0.48 for micronutrients, with higher value for calcium (0.75). There were small proportions of grossly misclassified nutrient intakes, while Bland-Altman plots indicated that the FFQ is accurate in assessing nutrient intake at a group level.
authors.affiliation: Universidade de São Paulo, Brasil. marlyac@usp.br
authors.forename: Marly Augusto
authors.initials: MA
authors.lastname: Cardoso
authors.forename: Luciana Yuki
authors.initials: LY
authors.lastname: Tomita
authors.forename: Elaine Cristina
authors.initials: EC
authors.lastname: Laguna
mesh_terms: D000328:Adult; D000368:Aged; D001938:Brazil; D004034:Diet Surveys / Q000379:methods / Q000592:standards*; D002149:Energy Intake / Q000502:physiology*; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008875:Middle Aged; D011203:Poverty; D011795:Surveys and Questionnaires / Q000592:standards*; D055815:Young Adult