Diagnostic Accuracy of Anthropometric Indices for Obesity Screening Among Asian Adolescents

Abstract

Introduction: Weight-and-height-based anthropometric indices have long been used for obesity screening among adolescents.However, the ability of their age-and-sex-specific reference values in classifying adolescent as “obese” in different populations was not fully established. Our study aimed to validate the existing international (BMI-for-age charts from WHO, CDC, IOTF) and local cut-offs [percent weight for height (PWH)] for obesity against body fat percentage, as assessed by 4 skinfolds measurement. Materials and Methods: A cross-sectional sample of 6991 adolescents aged 12 to 18 years was measured. All anthropometric measurements were compliant with the internationally accepted protocol. Obesity was defined as percentage body fat greater than or equal to 95 percentile, specific to age and sex. The validity of the existing classification criteria in detecting obesity was evaluated by comparing their respective diagnostic accuracy. Results: Both prevalence of obesity and diagnostic accuracy indices varied by the classification criteria. While all criteria generated very high specificity rates with the lowest being 95%, their sensitivity rates were low ranging from 43% to 71%. Youden’s index suggested that CDC and WHO criteria had optimal sensitivity and specificity. ROC analysis showed that overall performance could be improved by refining the existing cut-offs. Conclusions: Clinical validity of weight-and-height-based classification systems for obesity screening in Asian adolescents is poorer than expected, and this could be improved by refining the existing cut-offs. Key words: BMI-for-age references, Percentage body fat, Singapore, Validity, Weight-for height

Confronting the Obesity Epidemic: Call to Arms

“…Consequently, comparisons between countries are difficult, as 2 articles in this issue emphasise. 7,8 Both body composition and BMI change with age during childhood and adolescence, and therefore the BMI cut-offs used for defining overweight and obesity in adults cannot be applied directly to children and adolescents.…”

“…Whereas other surrogate measures of childhood adiposity are used, such as skinfold thickness, the percentage of ideal weight for height, or BMI standard deviation scores specific to the population, the cut-offs set for these measures are arbitrary; they are not based on biological data related to the risk of morbidity later in life. Deurenberg-Yap et al 7 compared the various surrogate measures recommended by international bodies, using a large set of data obtained from a local study of nearly 7000 adolescents. The authors concluded that while the different weight-and-height-based classification systems in Asian adolescents are of comparable validity, with high specificity values, their overall diagnostic accuracy is poorer than expected.…”

“…The authors concluded that while the different weight-and-height-based classification systems in Asian adolescents are of comparable validity, with high specificity values, their overall diagnostic accuracy is poorer than expected. Deurenberg-Yap et al 7 further suggest that sensitivity and positive predictive value, could both be improved by refining the existing cut-offs using data on percentage body fat and health risks.…”