title: Using cross-check questions to address the problem of mis-reporting of specific food groups on Food Frequency Questionnaires. UKWCS Steering Group. United Kingdom Women's Cohort Study Steering Group.
abstract: OBJECTIVE
  To explore the potential mis-reporting of specific food groups from food frequency questionnaire (FFQ) data and to examine the effect of using a weighting factor on estimated nutrient intake and ranking of subjects within the cohort according to nutrient intake.
  
  
  METHODS
  A weighting factor was calculated for each of the individual 6572 women aged 35-69 y for four food groups, fish, meat, vegetables and fruit, using FFQ data and cross-check responses.
  
  
  RESULTS
  The vegetables weighting had most effect on median intakes, particularly of fibre, vitamins A, C and E and folate. When all the weightings were applied, the median intakes of vitamins A and E were reduced by 35% and 27% respectively and the vitamin C intake was reduced by 44%. Ranking of subjects within the cohort according to nutrient intake was barely affected by the fish and meat weightings. The vegetable weighting had most effect on vitamin A with a rank correlation coefficient of 0.88. When all the weightings were applied the rank correlations for vitamins A, C and E and folate were all less than 0.90.
  
  
  CONCLUSIONS
  Inclusion of cross-check questions in FFQs can provide an additional source of information on food group intake. This can be compared with FFQ data to help identify possible over-reporting and then to adjust frequency of intake accordingly.
authors.affiliation: Division of Public Health, Nuffield Institute for Health, University of Leeds.
authors.forename: C
authors.initials: C
authors.lastname: Calvert
authors.forename: J
authors.initials: J
authors.lastname: Cade
authors.forename: J H
authors.initials: JH
authors.lastname: Barrett
authors.forename: A
authors.initials: A
authors.lastname: Woodhouse
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D001205:Ascorbic Acid / Q000008:administration & dosage; D004032:Diet; D002149:Energy Intake; D005189:False Positive Reactions; D005260:Female; D005399:Fishes; D005492:Folic Acid / Q000008:administration & dosage; D005502:Food; D005638:Fruit; D006801:Humans; D008460:Meat; D008875:Middle Aged; D011795:Surveys and Questionnaires; D014675:Vegetables; D014801:Vitamin A / Q000008:administration & dosage; D014810:Vitamin E / Q000008:administration & dosage
chemical_list: D014801:Vitamin A; D014810:Vitamin E; D005492:Folic Acid; D001205:Ascorbic Acid