title: Do aggregates of multiple questions better capture overall fish consumption than summary questions?
abstract: OBJECTIVE
  To compare intake estimates, validity and reliability of two summary questions to measure fish consumption with information from a detailed semi-quantitative food-frequency questionnaire (FFQ) on fish consumption.
  
  
  METHODS
  Population-based, cross-sectional study. Participants completed an FFQ and provided blood samples for erythrocyte membrane eicosapentaenoic acid (EPA) analysis. Aggregate measures of consumption of fresh/frozen/canned fish (fresh fish) and smoked/salted/dried fish (preserved fish) were generated from the FFQ and were compared with responses to the summary questions regarding intakes of similar items. Both methods were tested for validity, using correlation and linear regression techniques with EPA, and retest reliability.
  
  
  METHODS
  Perth metropolitan area, Western Australia.
  
  
  METHODS
  One hundred and nine healthy volunteers of both sexes, aged 21-75 years.
  
  
  RESULTS
  The summary fresh fish measure underestimated frequency and grams per week given by the aggregate question by about 50%, while estimates from the summary preserved fish measure were approximately three times that of the aggregate measure. Multiple linear regression analysis suggested that the aggregates accounted for more of the variation in EPA levels, but the difference was minimal. Intra-class correlations confirmed that both methods were reliable.
  
  
  CONCLUSIONS
  Our study indicates that extensive questioning results in different absolute intakes of fish compared with brief questioning, but does not add any information if ranking individuals according to overall consumption of fish.
authors.affiliation: School of Population Health M431, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia. Kym.Mina@uwa.edu.au
authors.forename: Kym
authors.initials: K
authors.lastname: Mina
authors.forename: Lin
authors.initials: L
authors.lastname: Fritschi
authors.forename: Matthew
authors.initials: M
authors.lastname: Knuiman
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D003430:Cross-Sectional Studies; D004910:Erythrocyte Membrane / Q000737:chemistry; D015525:Fatty Acids, Omega-3 / Q000032:analysis; D005247:Feeding Behavior; D005260:Female; D005399:Fishes; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D017747:Seafood; D011795:Surveys and Questionnaires; D014904:Western Australia
chemical_list: D015525:Fatty Acids, Omega-3