title: Predictive value of weight-for-age to identify overweight children.
abstract: OBJECTIVE
  The objective was to assess the predictive value of weight-for-age to identify overweight children and adolescents in the unusual research or public health situations where height is not available to calculate BMI.
  
  
  METHODS
  Data from the National Health and Nutrition Examination Survey 1999 to 2004 were used to calculate the sensitivity, specificity, and positive and negative predictive values of selected weight-for-age cut-off points to identify overweight children and adolescents (as defined by BMI >or=95th percentile). Positive and negative predictive values are dependent on prevalence and are reported here for this study population only.
  
  
  RESULTS
  The 50th and 75th weight-for-age percentiles had good sensitivity (100% and 99.6%, respectively), but poor positive predictive value (23.7% and 37.0%, respectively), while the 95th and 97th percentiles had reasonable positive predictive value (80.3% and 91.5%, respectively), but limited sensitivity (82.0% and 66.7%, respectively) to identify overweight subjects. The properties of weight-for-age percentiles to identify overweight subjects differed between sex, age, and race/ethnicity but remain within a relatively narrow range.
  
  
  CONCLUSIONS
  No single weight-for-age cut-off point was found to identify overweight children and adolescents with acceptable values for all properties and, therefore, cannot be used in the clinical setting. Furthermore, the positive predictive values reported here may be lower in populations with a lower prevalence of obesity. However, in unusual research or public health situations where height is not available, such as existing databases, weight-for-age percentiles may be useful to target limited resources to groups more likely to include overweight children and adolescents than the general population.
authors.affiliation: Division of Gastroenterology, Hepatology, and Nutrition, North 1559, Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104-4399, USA. nstettle@upenn.edu
authors.forename: Nicolas
authors.initials: N
authors.lastname: Stettler
authors.forename: Arezoo
authors.initials: A
authors.lastname: Zomorrodi
authors.forename: Jill C
authors.initials: JC
authors.lastname: Posner
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American; D000367:Age Factors; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D008297:Male; D009749:Nutrition Surveys; D050177:Overweight / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology*; D011237:Predictive Value of Tests; D015995:Prevalence; D012680:Sensitivity and Specificity; D012727:Sex Characteristics; D014481:United States; D044465:White People