title: Validity of self-reported weight, height and resultant body mass index in Chinese adolescents and factors associated with errors in self-reports.
abstract: BACKGROUND
  Validity of self-reported height and weight has not been adequately evaluated in diverse adolescent populations. In fact there are no reported validity studies conducted in Asian children and adolescents. This study aims to examine the accuracy of self-reported weight, height, and resultant BMI values in Chinese adolescents, and of the adolescents' subsequent classification into overweight categories.
  
  
  METHODS
  Weight and height were self-reported and measured in 1761 adolescents aged 12-16 years in a cross-sectional survey in Xi'an city, China. BMI was calculated from both reported values and measured values. Bland-Altman plots with 95% limits of agreement, Pearson's correlation and Kappa statistics were calculated to assess the agreement.
  
  
  RESULTS
  The 95% limits of agreement were -11.16 and 6.46 kg for weight, -4.73 and 7.45 cm for height, and -4.93 and 2.47 kg/m2 for BMI. Pearson correlation between measured and self-reported values was 0.912 for weight, 0.935 for height and 0.809 for BMI. Weighted Kappa was 0.859 for weight, 0.906 for height and 0.754 for BMI. Sensitivity for detecting overweight (includes obese) in adolescents was 56.1%, and specificity was 98.6%. Subjects' area of residence, age and BMI were significant factors associated with the errors in self-reporting weight, height and relative BMI.
  
  
  CONCLUSIONS
  Reported weight and height does not have an acceptable agreement with measured data. Therefore, we do not recommend the application of self-reported weight and height to screen for overweight adolescents in China. Alternatively, self-reported data could be considered for use, with caution, in surveillance systems and epidemiology studies.
authors.affiliation: From the Department of Epidemiology and Health Statistics, School of Public Health, Xi'an Jiaotong University College of Medicine, No,76 West Yanta Road, Xi'an, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zhou
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dibley
authors.forename: Yue
authors.initials: Y
authors.lastname: Cheng
authors.forename: Xue
authors.initials: X
authors.lastname: Ouyang
authors.forename: Hong
authors.initials: H
authors.lastname: Yan
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D002681:China; D006306:Health Surveys; D006801:Humans; D009765:Obesity; D050177:Overweight / Q000523:psychology; D057566:Self Report / Q000592:standards*
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