Development, validity and reproducibility of a dish-based semi-quantitative food frequency questionnaire in Iran

BACKGROUND: The food frequency questionnaire (FFQ) is the method of choice for dietary assessment in epidemiological studies. FFQs focusing on mixed-dishes and simple food items are useful where mixed-dishes are an essential part of food consumption. OBJECTIVE: Regarding the fact that the nature of the Iranian diet is mixed-dish, the present study aimed to design and assess the validity and reproducibility of a dish-based semi-quantitative FFQ in the Iranian adult population. METHODS: A list of 302 food items was collected from four geographical areas around Iran. The validation study was conducted on 97 healthy adults. The FFQ was introduced at the beginning of the study and 10 months after; two three-day food records were collected during the study. Also, biomarkers including 24-hour urinary potassium and nitrogen, serum retinol, and alpha-tocopherol were measured. RESULTS: A 142-food-item FFQ was concluded. The correlation coefficient between the second FFQ and the second three-day food record ranged from 0.225 to 0.323 for macronutrients and 0.128 to 0.476 for micronutrients. The percentile agreements (same or adjacent quartile) between the two methods were more than 60%for all nutrients. The intraclass correlation coefficient between FFQs (except for vitamin E) ranged from 0.363 to 0.578. The correlation coefficient between the second FFQ and the second biomarker assessment was 0.241 for protein.