The reliability of a food frequency questionnaire for use among adolescents.

ABSTRACT

BACKGROUND: Accurate measurement of dietary intake is essential for understanding the long-term effects of adolescent diet on chronic disease risk. However, adolescents may have limited food knowledge and ability to quantify portion sizes and recall dietary intake. Therefore, food frequency questionnaires (FFQs) deemed appropriate for use among adults may not be suitable for adolescents. OBJECTIVES: To evaluate an FFQ in comparison with a 3-day food record (FR) in 14-year olds participating in a population-based cohort study in Western Australia. METHODS: Nutrient intakes estimated by a semi-quantitative FFQ were compared with those from a 3-day FR using Bland & Altman limits of agreement (LOA), tertile classifications and Pearson's correlation coefficients. RESULTS: A total of 785 adolescents provided data from both dietary methods. Mean agreement between the FR and FFQ ranged from 73 (starch) to 161% (vitamin C). The LOA ranged from 27 (retinol) to 976% (carotene), with most nutrients being overestimated by the FFQ. For most nutrients, agreement between the two methods varied significantly with the magnitude of intake. Pearson's r ranged from 0.11 (polyunsaturated fats) to 0.52 (riboflavin). The FFQ classified 80 to 90% of subjects' nutrient intakes into the same or adjacent tertile as their FR. Boys performed slightly better for all of these indices. CONCLUSIONS: Agreement between individual FFQ and FR nutrient intakes was less than ideal. However, the FFQ was able to correctly rank a reasonable proportion of adolescents.