Severe Obesity and Cardiometabolic Risk in Children: Comparison from Two International Classification Systems

Objectives: There is no agreed-upon definition for severe obesity (Sev-OB) in children. We compared estimates of Sev-OB as defined by different cut-points of body mass index (BMI) from the Centers for Disease Control and Prevention (CDC) or the World Health Organization (WHO) curves and the ability of each set of cut-points to screen for the presence of cardiometabolic risk factors. Research Design and Methods: Cross-sectional, multicenter study involving 3,340 overweight/obese young subjects. Sev-OB was defined as BMI >= 99th percentile or >= 1.2 times the 95th percentile of the CDC or the WHO curves. High blood pressure, hypertriglyceridemia, low High Density Lipoprotein -cholesterol and impaired fasting glucose were considered as cardiometabolic risk factors. Results: The estimated prevalence of Sev-OB varied widely between the two reference systems. Either using the cut-point >= 99th percentile or >= 1.2 times the 95th percentile, less children were defined as Sev-OB by CDC than WHO (46.8 vs. 89.5%, and 63.3 vs. 80.4%, respectively p < 0.001). The CDC 99th percentile had lower sensitivity (58.5 vs 94.2), higher specificity (57.6 vs 12.3) and higher positive predictive value (34.4 vs 28.9) than WHO in identifying obese children with >= 2 cardiometabolic risk factors. These differences were mitigated using the 1.2 times the 95th percentile (sensitivity 73.9 vs. 88.1; specificity 40.7 vs. 22.5; positive predictive value 32.1 vs. 30.1). Substantial agreement between growth curves was found using the 1.2 times the 95th percentile, in particular in children <= 10 years. Conclusions: Estimates of Sev-OB and cardiometabolic risk as defined by different cut-points of BMI are influenced from the reference systems used. The 1.2 times the 95th percentile of BMI of either CDC or WHO standard has a discriminatory advantage over the 99th percentile for identifying severely obese children at increased cardiometabolic risk, particularly under 10 years of age.