Application Of Receiver Operating Characteristic In The Formulation Of The Body Fat Screening Standards For Children And Adolescents

Purpose:This research summarizes the basic principles and application of ROC curve. Using the BF% reference standard as gold standard to explore the appropriate BMI, FMI, Quetelet Index and Rohrer’s Index cut-offs for Chinese children and adolescents from 6-18 years old. And then assessing the diagnostic performance of the cut-offs in Chinese children and adolescents’body fat screening by the screening test evaluation model.Discussing the value and significance of each indicators, and providing a reasonable basis for the ROC curve application in children and adolescents’body fat screening standards.Methods:The subject investigated is the students of primary and middle school and college in Beijing, there are 8950 children and adolescents totally,7722 samples are used to determine the cut-offs of obesity and the low body fat,1228 samples are used to assessing the cut-offs. The major methods are descriptive statistics, partial correlation analysis, ROC curve and so on.Results:1. There exist gender differences in the growth trend of body fat between boys and girls. The boys’ growth curves increase from 6-11 years old, then the curves decreased from 11-14 years old, after 14 years old, a slow growth trend and gradually tends to be stable. On the other hand, the girls’growth curves have been increasing during the 6～18 years old in body fat.2. There are significant correlation between BMI, FMI, Quetelet Index, Rohrer’s Index and BF%, the descending order of the correlation coefficient is FMI, Rohrer’s Index, BMI and Quetelet Index.3. Contrasting the diagnostic performance of two different BMI values to diagnose obesity, one is WGOC recommendations, and the other is obtained by using ROC curve. Two sets of the BMI values have essentially the same level in reliability and yield, while the cut-offs obtained by using ROC curve have a higher sensitivity in validity assessment.4. Contrasting the diagnostic performance of each indexes’ cut-offs, following the descending order:male obesity cut-offs (FMI, Rohrer’s Index, BMI, Quetelet Index), female obesity cut-offs (FMI, Rohrer’s Index and Quetelet Index, BMI), male low body fat cut-offs (FMI, Rohrer’s Index, Quetelet Index, BMI), female low body fat cut-offs (FMI, BMI, Quetelet Index and Rohrer’s Index).Conclusion:1. There is age and gender differences in BF%, BMI, FMI, Quetelet Index and Rohrer’s Index between boys and girls, so we should formulate children body composition evaluation standards by age-and sex-.2. BF% and FMI can be more truly reflect the status of body composition. So in the physical fitness measurement system, we should promote a further generalization of the FMI and the use of the BF%.3. We should consider the "health-related index" in the development of children and adolescent body fat screening standards, and should take improving sensitivity as principle. The ROC curve is a effective method to develop criterion-referenced standard, and this methods applying in children and adolescents obesity screening is feasible.