title: The reliability and validity of a short food frequency questionnaire among 9-11-year olds: a multinational study on three middle-income and high-income countries.
abstract: OBJECTIVE
  The main aim of this study was to assess the reliability and validity of a food frequency questionnaire with 23 food groups (I-FFQ) among a sample of 9-11-year-old children from three different countries that differ on economical development and income distribution, and to assess differences between country sites. Furthermore, we assessed factors associated with I-FFQ's performance.
  
  
  METHODS
  This was an ancillary study of the International Study of Childhood Obesity, Lifestyle and the Environment. Reliability (n=321) and validity (n=282) components of this study had the same participants. Participation rates were 95% and 70%, respectively. Participants completed two I-FFQs with a mean interval of 4.9 weeks to assess reliability. A 3-day pre-coded food diary (PFD) was used as the reference method in the validity analyses. Wilcoxon signed-rank tests, intraclass correlation coefficients and cross-classifications were used to assess the reliability of I-FFQ. Spearman correlation coefficients, percentage difference and cross-classifications were used to assess the validity of I-FFQ. A logistic regression model was used to assess the relation of selected variables with the estimate of validity. Analyses based on information in the PFDs were performed to assess how participants interpreted food groups.
  
  
  RESULTS
  Reliability correlation coefficients ranged from 0.37 to 0.78 and gross misclassification for all food groups was <5%. Validity correlation coefficients were below 0.5 for 22/23 food groups, and they differed among country sites. For validity, gross misclassification was <5% for 22/23 food groups. Over- or underestimation did not appear for 19/23 food groups. Logistic regression showed that country of participation and parental education were associated (P⩽0.05) with the validity of I-FFQ. Analyses of children's interpretation of food groups suggested that the meaning of most food groups was understood by the children.
  
  
  CONCLUSIONS
  I-FFQ is a moderately reliable method and its validity ranged from low to moderate, depending on food group and country site.
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki , Helsinki, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Saloheimo
authors.affiliation: School of Medicine, Universidad de los Andes , Bogotá, Colombia.
authors.forename: S A
authors.initials: SA
authors.lastname: González
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki , Helsinki, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Erkkola
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University System , Baton Rouge, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Milauskas
authors.affiliation: Department of Industrial Engineering, Faculty of Engineering, Universidad de los Andes, CeiBA Complex Systems Research Center , Bogotá, Colombia.
authors.forename: J D
authors.initials: JD
authors.lastname: Meisel
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University System , Baton Rouge, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Champagne
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, USA; Department of Kinesiology, University of Massachusetts Amherst, Amherst, USA.
authors.forename: C
authors.initials: C
authors.lastname: Tudor-Locke
authors.affiliation: School of Medicine, Universidad de los Andes , Bogotá, Colombia.
authors.forename: O
authors.initials: O
authors.lastname: Sarmiento
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University System , Baton Rouge, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Katzmarzyk
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki , Helsinki, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Fogelholm