title: Optimal waist-to-height ratio values for cardiometabolic risk screening in an ethnically diverse sample of South African urban and rural school boys and girls.
abstract: BACKGROUND
  The proposed waist-to-height ratio (WHtR) cut-off of 0.5 is less optimal for cardiometabolic risk screening in children in many settings. The purpose of this study was to determine the optimal WHtR for children from South Africa, and investigate variations by gender, ethnicity and residence in the achieved value.
  
  
  METHODS
  Metabolic syndrome (MetS) components were measured in 1272 randomly selected learners, aged 10-16 years, comprising of 446 black Africans, 696 mixed-ancestry and 130 Caucasians. The Youden's index and the closest-top-left (CTL) point approaches were used to derive WHtR cut-offs for diagnosing any two MetS components, excluding the waist circumference.
  
  
  RESULTS
  The two approaches yielded similar cut-off in girls, 0.465 (sensitivity 50.0, specificity 69.5), but two different values in boys, 0.455 (42.9, 88.4) and 0.425 (60.3, 67.7) based on the Youden's index and the CTL point, respectively. Furthermore, WHtR cut-off values derived differed substantially amongst the regions and ethnic groups investigated, whereby the highest cut-off was observed in semi-rural and white children, respectively, Youden's index0.505 (31.6, 87.1) and CTL point 0.475 (44.4, 75.9).
  
  
  CONCLUSIONS
  The WHtR cut-off of 0.5 is less accurate for screening cardiovascular risk in South African children. The optimal value in this setting is likely gender and ethnicity-specific and sensitive to urbanization.
authors: Department of Biomedical Technology, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Cape Town, South Africa. matshat@cput.ac.za
authors: Tandi E
authors: TE
authors: Matsha
authors: Andre-Pascal
authors: AP
authors: Kengne
authors: Yandiswa Y
authors: YY
authors: Yako
authors: Gloudina M
authors: GM
authors: Hon
authors: Mogamat S
authors: MS
authors: Hassan
authors: Rajiv T
authors: RT
authors: Erasmus
mesh_terms: D000293:Adolescent; D001827:Body Height; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000453:epidemiology*; D012372:ROC Curve; D012016:Reference Values; D012424:Rural Population; D013019:South Africa / Q000453:epidemiology / Q000208:ethnology; D014505:Urban Population; D055105:Waist Circumference
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