title: Reproducibility and validity of a food-frequency questionnaire for use among low-income Brazilian workers.
abstract: OBJECTIVE
  To assess the reproducibility and validity a 127-item, habitual intake, food-frequency questionnaire (FFQ), developed for low-income and low-literacy Brazilian workers, by comparison with a 24-hour dietary recall (24-HDR).
  
  
  METHODS
  The FFQ and 24-HDR were interviewer-administered at the local workplace to each subject twice, with a period of 6 months between estimates; and four 24-HDRs were conducted during the 4-month period between the two FFQs (FFQ1 and FFQ2). Reproducibility was tested by comparing mean nutrient intakes from the two FFQs. Validity was determined by comparing the mean nutrient intakes from the FFQs with the corresponding averages of the six 24-HDRs (reference method).
  
  
  METHODS
  Goiânia City, in Central West Brazil.
  
  
  METHODS
  The study was based on 104 (62 women and 42 men) subjects, aged 18 to 60 years, who were randomly selected.
  
  
  RESULTS
  Dietary intake from the FFQ was higher than from the 24-HDR. Reproducibility was assessed by Pearson correlation coefficients for nutrients from FFQ1 and FFQ2, and ranged from 0.23 for retinol to 0.69 for total energy (mean 0.52). Intra-class coefficients for nutrients averaged by the 24-HDRs ranged from 0.29 for vitamin C to 0.76 for total energy; retinol was not significant. In the validation study, correlation between the FFQ and the 24-HDR ranged between 0.21 for vitamin C and 0.70 for total energy (mean 0.50). Adjusting for total energy lowered the coefficients, except for calcium, retinol and vitamin C. Coefficients increased with attenuation, ranging from 0.35 for carbohydrate to 0.65 for calcium.
  
  
  CONCLUSIONS
  Results indicate that this questionnaire had satisfactory reproducibility and reasonable validity.
authors.affiliation: Faculdade de Nutrição, Universidade Federal de Goiás, Brazil. nelida@fanut.ufg.br
authors.forename: Nélida Schmid
authors.initials: NS
authors.lastname: Fornés
authors.forename: Maria Luiza Ferreira
authors.initials: ML
authors.lastname: Stringhini
authors.forename: Berenice Müller
authors.initials: BM
authors.lastname: Elias
mesh_terms: D000328:Adult; D001938:Brazil; D015930:Diet Records; D004034:Diet Surveys; D002149:Energy Intake; D005247:Feeding Behavior; D005260:Female; D005504:Food Analysis; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008875:Middle Aged; D015596:Nutrition Assessment; D009753:Nutritive Value; D009790:Occupations / Q000145:classification; D011203:Poverty; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires