Using weight-for-age percentiles to screen for overweight and obese children and adolescents

There are relatively low rates of screening for overweight and obesity among children and adolescents in primary care. A simplified method for such screening is needed. The study objective was to examine if weight-for-age percentiles are sufficiently sensitive in identifying overweight and obesity in children and adolescents. We used data from two distinct sources: four consecutive cycles of the National Health and Nutrition Examination Surveys (NHANES) from the years 2005 to 2012, using participants aged 2-17.9 years for whom data on age, sex, weight, and height were available (n = 12,884), and primary care clinic measurements (n = 15,152). Primary outcomes were the threshold values of weight-for-age percentiles which best discriminated between normal weight, overweight, and obesity status.Receiver operating characteristic analyses demonstrated that weight-for-age percentiles well discriminated between normal weight and overweight and between non-obese and obese individuals (area under curve = 0.956 and 0.977, respectively, both p< 0.001). Following Classification and Regression Trees analysis, the 90th and 75th weight-for-age percentiles were chosen as appropriate cutoffs for obesity and overweight, respectively. These cutoffs had high sensitivity and negative predictive value in identifying obese participants (94.3% and 98.6%, respectively, for the 90th percentile) and in identifying overweight participants (93.2% and 95.9%, respectively, for the 75th percentile). The sensitivities and specificities were nearly identical across race and sex, and in the validation data from NHANES 2011 to 2012 and primary care. We conclude that weight-for-age percentiles can discriminate between normal weight, overweight and obese children, and adolescents. The 75th and 90th weight-for-age percentiles correspond well with the BMI cutoffs for pediatric overweight and obesity, respectively.