Validity of self-reported height, weight, and body mass index of the Korea Youth Risk Behavior Web-based Survey questionnaire.
OBJECTIVE
Self-reported anthropometric values, such as height and weight, are used to calculate body mass index (BMI) and assess the prevalence of obesity among adolescents. The aim of this study was to evaluate the validity of self-reported height, weight, and BMI of the Korea Youth Risk Behavior Web-based Survey questionnaire.


METHODS
A convenience sample of 137 middle school students and 242 high school students completed a self-administered questionnaire in 2008. Body height and weight were directly measured after self-reported values were obtained from the questionnaire survey. Sensitivity, specificity, and kappa statistics were computed in order to evaluate the validity of the prevalence of obesity (BMI ≥ 95th percentile or ≥ 25 kg/m(2)) based on self-reported data.


RESULTS
Self-reported weight and BMI tended to be underestimated. Self-reported height tended to be overestimated among middle school females and high school males. Obese adolescents tended to underestimate their weight and BMI and overestimate their height more than non-obese adolescents. The prevalence estimate of obesity based on self-reported data (10.6%) was lower than that based on directly measured data (15.3%). The estimated sensitivity of obesity based on self-reported data was 69.0% and the specificity was 100.0%. The value of kappa was 0.79 (95% confidence interval, 0.70-0.88).


CONCLUSIONS
This study demonstrated that self-reported height and weight may lead to the underestimation of BMI and consequently the prevalence of obesity. These biases should be taken into account when self-reported data are used for monitoring the prevalence and trends of obesity among adolescents nationwide.
Department of Preventive Medicine, Catholic University of Daegu School of Medicine, Korea.
Jisuk
J
Bae
Hyojee
H
Joung
Jong Yeon
JY
Kim
Kyoung Nam
KN
Kwon
Yoonjung
Y
Kim
Soon Woo
SW
Park
D000293:Adolescent; D000294:Adolescent Behavior; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D016001:Confidence Intervals; D003625:Data Collection; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000453:epidemiology*; D015995:Prevalence; D056910:Republic of Korea; D012309:Risk-Taking; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires