Validation of an FFQ and options for data processing using the doubly labelled water method in children.

Objective: To validate an FFQ designed to estimate energy intake in children against doubly labelled water (DLW). To investigate how quality control and standard beverage portion sizes affect the validity of the FFQ. Design: Thirty healthy children, aged 4-6 years, participated. Total energy expenditure (EE) was measured by the DLW method during an observation period of 15 d. At the end of this period parents filled out an FFQ designed to assess the child's habitual energy intake (El) of the preceding four weeks. Setting: Validation study in The Netherlands. Subjects: Thirty healthy children (fifteen boys and fifteen girls), aged 4-6 years. Results: Mean El (6117 (SD 1025) kJ/d) did not differ significantly from mean EE (6286 (SD 971) kJ/d; P = 0.15); the mean EI:EE ratio was 0.98. The Pearson correlation coefficient between El and EE was 0.62. The Bland-Altman plot showed no systematic bias and a constant bias close to zero. Less intensive quality control of the FFQ maintained the mean EI:EE ratio and decreased the correlation slightly. Using standard instead of individually measured beverage portion sizes decreased the mean EI:EE ratio, but maintained the correlation. Conclusions: It can be concluded that the developed FFQ is a valid instrument to estimate mean energy intake in a group of 4- to 6-year-old children and performs reasonably well to rank the subjects with respect to energy intake. It is therefore a useful instrument to estimate energy intake in children in surveys and epidemiological studies in The Netherlands.