title: Relative validity of a semi-quantitative, web-based FFQ used in the 'Snart Forældre' cohort - a Danish study of diet and fertility.
abstract: OBJECTIVE
  To assess the relative validity of a semi-quantitative, web-based FFQ completed by female pregnancy planners in the Danish 'Snart Forældre' study.
  
  
  METHODS
  We validated a web-based FFQ based on the FFQ used in the Danish National Birth Cohort against a 4 d food diary (FD) and assessed the relative validity of intakes of foods and nutrients. We compared means and medians of intakes, and calculated Pearson correlation coefficients and de-attenuated coefficients to assess agreement between the two methods. We also calculated the proportion correctly classified based on the same or adjacent quintile of intake and the proportion of grossly misclassified (extreme quintiles).
  
  
  METHODS
  Participants (n 128) in the 'Snart Forældre' study who had completed the web-based FFQ were invited to participate in the validation study.
  
  
  METHODS
  Participants in the 'Snart Forældre' study, in total ninety-seven women aged 20-42 years.
  
  
  RESULTS
  Reported intakes of dairy products, vegetables and potatoes were higher in the FFQ compared with the FD, whereas reported intakes of fruit, meat, sugar and beverages were lower in the FFQ than in the FD. Overall the de-attenuated correlation coefficients were acceptable, ranging from 0·33 for energy to 0·93 for vitamin D. The majority of the women were classified in the same or adjacent quintile and few women were misclassified (extreme quintiles).
  
  
  CONCLUSIONS
  The web-based FFQ performs well for ranking women of reproductive age according to high or low intake of foods and nutrients and, thus, provides a solid basis for investigating associations between diet and fertility.
authors.affiliation: 1Division of Nutrition,National Food Institute,Technical University of Denmark,Mørkhøj Bygade 19,2860 Søborg,Denmark.
authors.forename: Vibeke K
authors.initials: VK
authors.lastname: Knudsen
authors.affiliation: 2Department of Epidemiology,Boston University School of Public Health,Boston,MA,USA.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Hatch
authors.affiliation: 3Department of Clinical Epidemiology,Aarhus University Hospital,Aarhus,Denmark.
authors.forename: Heidi
authors.initials: H
authors.lastname: Cueto
authors.affiliation: 4Department of Clinical Laboratory & Nutritional Sciences,University of Massachusetts Lowell,Lowell,MA,USA.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Tucker
authors.affiliation: 2Department of Epidemiology,Boston University School of Public Health,Boston,MA,USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Wise
authors.affiliation: 1Division of Nutrition,National Food Institute,Technical University of Denmark,Mørkhøj Bygade 19,2860 Søborg,Denmark.
authors.forename: Tue
authors.initials: T
authors.lastname: Christensen
authors.affiliation: 3Department of Clinical Epidemiology,Aarhus University Hospital,Aarhus,Denmark.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Mikkelsen
mesh_terms: D000328:Adult; D001628:Beverages; D003611:Dairy Products; D003718:Denmark; D004032:Diet; D015930:Diet Records; D000072001:Diet, Healthy; D002149:Energy Intake; D005260:Female; D005298:Fertility; D005500:Follow-Up Studies; D005638:Fruit; D006801:Humans; D020407:Internet; D008019:Life Style; D008460:Meat; D018977:Micronutrients / Q000008:administration & dosage / Q000032:analysis; D064427:Nutritive Sweeteners / Q000008:administration & dosage; D011446:Prospective Studies; D015203:Reproducibility of Results; D011198:Solanum tuberosum; D011795:Surveys and Questionnaires; D014675:Vegetables; D014807:Vitamin D / Q000008:administration & dosage / Q000032:analysis; D055815:Young Adult
chemical_list: D018977:Micronutrients; D064427:Nutritive Sweeteners; D014807:Vitamin D
keywords: Fecundity; Pre-pregnancy; Relative validity; Web-based FFQ