Estimating dietary intakes from a brief questionnaire: A simulation study of reliability in a molecular epidemiologic study of pancreatic and biliary diseases.

INTRODUCTION: Brief dietary questionnaires may be useful in research or clinical settings where in-depth assessments are inefficient or impractical. We conducted a simulation study to assess the reliability of a brief food frequency questionnaire (bFFQ) for capturing dietary intakes relative to a detailed survey. SUBJECTS AND METHODS: The bFFQ was used in a study of patients with pancreatic and biliary diseases in eastern Spain (n = 605). The structured interview included a section probing the frequency of intakes of 14 food groups, using 4 response categories. Data from a 93-item semi-quantitative food frequency questionnaire (SFFQ) with 9 response categories (n = 1337) was used to: (1) develop estimates of nutrient intakes for each food group, and (2) to simulate how intakes would have been estimated using the bFFQ. The simulation allowed to assess effects of aggregating foods and using abbreviated frequency categories.
RESULTS: Correlations between actual and simulated intake frequencies exceeded 0.70 for 10 food groups; modest correlations (0.43-0.56) were observed for groups assessed less well using abbreviated frequency categories. Correlations exceeded 0.60 for most nutrients. Concordance was lower for several nutrients, notably retinol, for which substantial proportions were contributed by groups combining foods with highly variable levels of these compounds.
CONCLUSIONS: Intake estimates from the bFFQ may be useful in exploratory analyses of the role of diet in bilio-pancreatic diseases and related etiopathogenic events. Estimates for some nutrients may be less reliable, and should be interpreted with particular caution.