title: Validity and reproducibility of a web-based, self-administered food frequency questionnaire.
abstract: OBJECTIVE
  To assess the validity and the reproducibility of a newly developed web-based, self-administered food frequency questionnaire (web-FFQ).
  
  
  METHODS
  A total of 74 healthy subjects (34 men and 40 women) from the Québec City metropolitan area were asked to complete, in random order, the web-FFQ, a validated interviewer-administered FFQ (IA-FFQ) and a 3-day food record (3-day FR).
  
  
  RESULTS
  Mean intakes of 17/22 nutrients assessed between the web-FFQ and the 3-day FR were not significantly different (differences <10%, P≥0.11). Sex and energy-adjusted de-attenuated Pearson correlation coefficients for each nutrient varied from 0.12-0.98 (mean R=0.55, 95% confidence interval 0.46; 0.63) between the web-FFQ and the 3-day FR. All correlations were significant (P≤0.01) and above 0.34 (mean R=0.59, 95% confidence interval 0.54; 0.65) between the web-FFQ and the IA-FFQ, except for sodium (R=0.17, P=0.14). Cross-classification analysis revealed that on average, 77% of subjects were classified in the same or adjacent quartile of nutrient intake between the web-FFQ and the 3-day FR. Correlation coefficients for reproducibility of the web-FFQ tested 4-6 weeks apart in the same individuals were all equal or above 0.48 (P≤0.0001; mean R=0.72, 95% confidence interval 0.68; 0.76). More than 90% of the subjects were classified in the same or adjacent quartile between the two administrations of the web-FFQ, while only 0.8% was misclassified.
  
  
  CONCLUSIONS
  These data demonstrate that the newly developed web-based FFQ appears to have reasonable validity and good reproducibility for assessing nutrient intakes at the group and individual levels in a population of healthy adults.
authors.affiliation: Institute of Nutraceuticals and Functional Foods, Laval University, Québec, QC, Canada.
authors.forename: M-È
authors.initials: MÈ
authors.lastname: Labonté
authors.forename: A
authors.initials: A
authors.lastname: Cyr
authors.forename: L
authors.initials: L
authors.lastname: Baril-Gravel
authors.forename: M-M
authors.initials: MM
authors.lastname: Royer
authors.forename: B
authors.initials: B
authors.lastname: Lamarche
mesh_terms: D000328:Adult; D004032:Diet; D015930:Diet Records; D004034:Diet Surveys / Q000379:methods / Q000592:standards*; D002149:Energy Intake; D005260:Female; D006801:Humans; D020407:Internet; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*; D055815:Young Adult