Reliability and relative validity of a quantitative food-frequency questionnaire for use among adults in Italian population.

Our objective was to assess the reliability and relative validity of a food frequency questionnaire (FFQ) among adult people. In a cross-sectional study carried out in northern Italy, 112 adults were recruited. A total of 189 food and drink items were selected according to those typically consumed by Italians. FFQ reliability was assessed by two repeated administrations at 6 weeks. The FFQ was validated using four 24-h recalls repeated in the same period of time. For the validation study, classification into quartiles from the two methods and Bland-Altman plot were also performed. The reliability study showed a good correlation between the two methods. Bland-Altman plots showed that the two methods are very likely to agree for individual energy and macronutrient intakes. The reliability and relative validity of this FFQ was good, supporting its use in assessing dietary intakes of Italians in nutritional surveillance programs and in epidemiological dietary surveys.