title: A proposed cutoff point of waist-to-height ratio for metabolic risk in African township adolescents.
abstract: OBJECTIVE
  A waist:height ratio (WHtR) higher than 0.5 has been proposed as a cutoff point for abdominal obesity in both sexes and at all ages. It is unknown if this cutoff point is appropriate for previously undernourished adolescents. We assessed the cutoff value of the WHtR associated with an increased metabolic risk in 178 black South African 14- to 18-y-old adolescents (69 boys, 109 girls).
  
  
  METHODS
  We measured weight, height, waist circumference, fasting plasma glucose and insulin levels, serum high-sensitivity C-reactive protein, and blood pressure and calculated the WHtR and homeostasis model assessment of insulin resistance (HOMA-IR). Using receiver operating characteristics curve analyses, we assessed the WHtR with the highest sensitivity and specificity to discriminate adolescents with increased fasting plasma glucose, HOMA-IR, serum high-sensitivity C-reactive protein, and blood pressure from those with "normal" values.
  
  
  RESULTS
  The WHtR cutoff points derived from the receiver operating characteristics curves ranged from 0.40 to 0.41, with best diagnostic value at 0.41. A WHtR of 0.40 had 80% sensitivity and 38.5% specificity to classify adolescents with fasting blood glucose level higher than 5.6 mmol/L (area under the curve [AUC] 0.57). A WHtR of 0.41 had 64% sensitivity and 58.5% specificity for a HOMA-IR higher than 3.4 (AUC 0.66), 55% sensitivity and 55.6% specificity for a high-sensitivity C-reactive protein level higher than 1 mg/L (AUC 0.57), and 64% sensitivity and 50.2% specificity for a blood pressure higher than the age-, sex-, and height-specific 90th percentiles (AUC 0.56). Adolescents with a WHtR higher than 0.41 had an odds ratio of 2.46 (95% confidence interval 0.96-6.30) for having a HOMA-IR higher than 3.4.
  
  
  CONCLUSIONS
  The WHtR cutoff to indicate metabolic risk for black South African adolescents is 0.41, which is lower than the proposed international cutoff of 0.5. The WHtR can be used for screening adolescents with components of the metabolic syndrome in intervention programs.
authors.affiliation: Centre of Excellence for Nutrition, North-West University, Potchefstroom, South Africa. salome.kruger@nwu.ac.za
authors.forename: H Salome
authors.initials: HS
authors.lastname: Kruger
authors.forename: Mieke
authors.initials: M
authors.lastname: Faber
authors.forename: Aletta E
authors.initials: AE
authors.lastname: Schutte
authors.forename: Suria M
authors.initials: SM
authors.lastname: Ellis
mesh_terms: D000293:Adolescent; D044383:Black People; D001786:Blood Glucose / Q000032:analysis; D001794:Blood Pressure; D001827:Body Height; D015992:Body Mass Index; D002097:C-Reactive Protein; D005215:Fasting; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D044342:Malnutrition; D024821:Metabolic Syndrome / Q000175:diagnosis*; D012016:Reference Values; D012680:Sensitivity and Specificity; D013019:South Africa; D055105:Waist Circumference
chemical_list: D001786:Blood Glucose; D002097:C-Reactive Protein