Reproducibility and comparative validity of a food frequency questionnaire for Australian adults

Background: Food frequency questionnaires (FFQ) are used in epidemiological studies to investigate the relationship between diet and disease. There is a need for a valid and reliable adult FFQ with a contemporary food list in Australia. Aims: To evaluate the reproducibility and comparative validity of the Australian Eating Survey (AES) FFQ in adults compared to weighed food records (WFRs). Methods: Two rounds of AES and three-day WFRs were conducted in 97 adults (31 males, median age and BMI for males of 44.9 years, 26.2 kg/m2, females 41.3 years, 24.0 kg/m2. Reproducibility was assessed over six months using Wilcoxon signed-rank tests and comparative validity was assessed by intraclass correlation coefficients (ICC) estimated by fitting a mixed effects model for each nutrient to account for age, sex and BMI to allow estimation of between and within person variance. Results: Reproducibility was found to be good for both WFR and FFQ since there were no significant differences between round 1 and 2 administrations. For comparative validity, FFQ ICCs were at least as large as those for WFR. The ICC of the WFR-FFQ difference for total energy intake was 0.6 (95% CI 0.43, 0.77) and the median ICC for all nutrients was 0.47, with all ICCs between 0.15 (%E from saturated fat) and 0.7 (g/day sugars). Conclusions: Compared to WFR the AES FFQ is suitable for reliably estimating the dietary intakes of Australian adults across a wide range of nutrients