REPRODUCIBILITY AND RELATIVE VALIDITY OF ENERGY AND MACRONUTRIENT INTAKE OF A FOOD FREQUENCY QUESTIONNAIRE DEVELOPED FOR THE GERMAN PART OFTHE EPIC PROJECT

Background. For use in the German part of the European Prospective Inv estigation into Cancer and Nutrition (EPIC) a self-administered, optic ally readable food frequency questionnaire (FFQ) was developed to asse ss individuals' usual food and nutrient intake over the past year. The food list comprised 158 food items for which the typical portion size , the consumption frequency (1-6 times) and the time period (day, week , month, or year) were requested, This paper reports the results of th e reproducibility and relative validity of nutrient intakes obtained b y this instrument. Methods. The study was carried out from October 199 1 to October 1992. During this period, 104 men and women, aged 35-64 y ears, completed a 24-hour recall once a month, and the FFQ in the midd le and at the end of this study. A short questionnaire on global consu mption patterns was used to adjust the food consumption frequency give n in the FFQ. Results. Reproducibility correlations varied from 0.59 f or saturated fat to 0.88 for alcohol, with most values falling between 0.60 and 0.70. Energy-adjustment decreased the observed correlations for all nutrients. Correlations between nutrient intake values from th e 12-day average of dietary recalls and the FFQ corrected for food con sumption frequency ranged from 0.42 for polyunsaturated fat to 0.88 fo r alcohol, followed by 0.65 for dietary fibres. After de-attenuation a nd energy-adjustment the range of correlations was somewhat wider (0.4 3-0.75, without alcohol). With regard to classification, on average, 3 6% of subjects fell into the same quintile, and 75% into within-one qu intile when classified by the frequency-corrected FFQ compared to the quintiles based on recalled data. Conclusions. In summary, the newly d eveloped FFQ showed fairly good reproducibility and relative validity for most evaluated nutrients. The between-subject variation of nutrien ts in the German cohort (including the participants from East Germany) is likely to be greater than that among the subjects of the pilot pha se. A revised version of the FFQ corrected for food consumption freque ncy is used in the EPIC study.