Reproducibility and Validity of a Semi-Quantitative Food Frequency Questionnaire for Children Aged 6-12 in Western China

The Food Frequency Questionnaire (FFQ) is often used to assess dietary intake in large-scale epidemiological studies. This study aimed to evaluate the reproducibility and validity of the FFQ newly developed for children aged 6 to 12 in western China. A total of 133 children were included in the analysis, and all the children and their caregivers completed the FFQs twice with a three-month interval period, and three 24 h recalls were carried out one month after the first FFQ. We assessed the relative validity and reproducibility using various methods, such as the Spearman correlation coefficient, intra-class correlation coefficient, weighed Kappa, quartile agreement, and Bland-Altman analysis. The Spearman correlation coefficients for food ranged from 0.30 to 0.84, and for nutrients from 0.46 to 0.82 regarding reproducibility. The food intra-class correlation coefficients ranged from 0.20 to 0.85, while nutrients' ranged from 0.37 to 0.75. In terms of relative validity, the average Spearman correlation coefficients for food were 0.20, and 0.30 for energy and nutrients. The energy-adjusted and de-attenuation coefficients were calculated. Moreover, the average percentage of participants misclassified into the extreme quartile for food and nutrients was 8.0% and 7.0%, respectively. Weighted Kappa values indicated acceptable agreement between the FFQs and 24 h recalls. Furthermore, the percentage of results in the limits of agreement (LOA) were all above 93.0%. In conclusion, The FFQ showed good reproducibility and acceptable relative validity for assessing the dietary intake of children aged 6-12 in western China.