USING CROSS-CHECK QUESTIONS TO ADDRESS THE PROBLEM OF MIS-REPORTING OF SPECIFIC FOOD GROUPS ON FOOD FREQUENCY QUESTIONNAIRES

Objective: To explore the potential mis-reporting of specific food gro ups from food frequency questionnaire (FFQ) data and to examine the ef fect of using a weighting factor on estimated nutrient intake and rank ing of subjects within the cohort according to nutrient intake. Design and subjects: A weighting factor was calculated for each of the indiv idual 6572 women aged 35-69 y for four food groups, fish, meat, vegeta bles and fruit, using FFQ data and cross-check responses. Results: The vegetable weighting had most effect on median intakes, particularly o f 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% an d 27% respectively and the vitamin C intake was reduced by 44%. Rankin g of subjects within the cohort according to nutrient intake was barel y affected by the fish and meat weightings. The vegetable weighting ha d most effect an vitamin A with a rank correlation coefficient of 0.88 . When all the weightings were applied the rank correlations for vitam ins A, C and E and folate were all less than 0.90, Conclusion: Inclusi on of cross-check questions in FFQs can provide an additional source o f information an food group intake. This can be compared with FFQ data to help identify possible over-reporting and then to adjust frequency of intake accordingly.