VALIDITY AND REPRODUCIBILITY OF A FOOD FREQUENCY QUESTIONNAIRE TO ASSESS DIETARY-INTAKE OF WOMEN LIVING IN MEXICO-CITY

Objective. To assess the reproducibility and validity of a 116 item se mi-quantitative food frequency questionnaire (FFQ), designed to assess the relation between dietary intake and chronic diseases. Material an d methods. To test the reproducibility of the FFQ questionnaire, the F FQ was administered twice to 134 women residing in Mexico City at an i nterval of approximately one year; to assess the validity we compared results obtained by the FFQs with those obtained by four 4-day 24-hour recalls at three month intervals. Validity and reproducibility were e valuated using regression analysis and Pearson and intraclass correlat ion coefficients of log-e and calorie-adjusted nutrient scores. Result s. Mean values for intake of most nutrients assessed by the two food f requency questionnaires were similar. However, means for the 24-hr rec all were significantly lower. Intraclass correlation coefficients for nutrient intakes, assessed by questionnaires, administered one year ap art, ranged from 0.38 for cholesterol to 0.54 for crude fiber. Correla tion coefficients between energy-adjusted nutrient intakes, measured b y diet recalls, and the first FFQ ranged from 0.12 for polyunsaturated fatty acids to 0.67 for saturated fatty acids. Regression coefficient s between 24-hr recall and FFQ,s were all significant were significant for all nutrients, except for polyunsaturated fat, folic acid, vitami n E and Zinc, Conclusions. These data indicate that this semi-quantita tive FFQ is reproducible and provides a useful estimate by which to ca tegorize individuals by level of past nutrient intake. However, its ap plication outside Mexico City or in different age and gender populatio ns will require additional modifications and validation efforts.