Background: The adiposity measurement by reliable methods such as dual X-ray absorptiometry (DXA) is not feasible in routine medical care and instead of this, the anthropometric methods are used. However, these methods could be inaccurate to estimate the body fat content. Additionally, in pediatric patients, some anthropometric indexes requires percentiles or Z-scores for their interpretation, like the body mass index (BMI) or the waist circumference (WC). Although anthropometric indexes with a single cut-off point, such as tri-ponderal index (TMI [weight/height3]) or waist-to-height ratio (WHtR) have been proposed as an alternative to adiposity assessment, it is important to evaluate their accuracy.
Objective: To evaluate different anthropometric methods to estimate body fat percent by DXA (bfDXA) in children and adolescents.
Methods: We conducted a cross-sectional study. We included 1,513 participants between 5 to 18 years old. We measure weight, height and WC by standardized methods and BMI, TMI and WHtR were calculated. The adiposity was evaluated by whole body less head DXA. A linear regression analysis was performed to estimate bfDXA. We also analyzed ROC curves for the detection of overweight/obesity (≥p85 bfDXA) and we identified the optimal cut-off value for TMI. We compare the diagnostic performance of BMIZ, WC, WHtR and TMI.
Results: We identified a R2 between 0.28 to 0.76 with the different anthropometric methods in males and 0.51 to 0.66 in females. The WC had the lowest values of R2 while TMI, BMIZ and WHtR explained a higher variance of bfDXA. The areas under the curve to detect overweight/obesity were found between 0.92 and 0.95 for TMI, BMIZ and WHtR in both genders, without significant differences between them. We identified a TMI≥15.2 kg/m3 in both genders as an optimal cut-off value. Table 1 shows the diagnostic performance to detect overweight/obesity for each anthropometric index.
|Anthropometric index||Sensitivity||Specificity||% Adequate classification||Sensitivity||Specificity||% Adequate classification|
|TMI cut-off previously reporteda||74||93||91||65||93||89|
|TMI (≥15.2 kg/m3)||87||89||88||93||80||82|
|aMales: >16.0 kg/m3; females: >16.8 kg/m3.|
Conclusion: TMI is an easy and acceptable tool to estimate the body fat in children and adolescents. TMI has a better diagnostic performance for an adequate classification of adiposity in comparison of BMIZ and WHtR.
27 - 29 Sep 2018
European Society for Paediatric Endocrinology