Comparison of different BMI cut-offs to screen for child and adolescent obesity in urban China

Objectives: To determine which set of BMI cut-offs is the most appropriate to define child and adolescent obesity in urban China. Design: A cross-sectional study was carried out between 1 November and 31 December in 2017. Setting: Community Healthcare Center in Minhang District, Shanghai, China. Participants: A total of 12 426 children and adolescents aged 7-17 years were selected by cluster random sampling. Bioelectrical impedance analysis was the gold standard to measure body composition. Results: Comparisons of three sets of BMI cut-offs by sensitivity and kappa value revealed that the Working Group on Obesity in China (WGOC) (sensitivity 39 center dot 9-84 center dot 0 %; kappa 0 center dot 51-0 center dot 79) and WHO (sensitivity 25 center dot 5-74 center dot 5 %; kappa 0 center dot 35-0 center dot 78) cut-offs were not superior to the International Obesity Task Force (IOTF) (sensitivity 47 center dot 9-92 center dot 4 %; kappa 0 center dot 58-0 center dot 85) cut-offs across all subgroups. The WGOC and WHO cut-offs yielded higher misclassification rates, in the worst case, categorising 11 center dot 2 % of girls with high adiposity as normal and 44 center dot 4 % of them as overweight, while the IOTF cut-offs categorised 2 center dot 3 % as normal and 30 center dot 7 % as overweight. Individuals who were classified by the IOTF cut-offs as overweight had the lowest ratios of high adiposity (4 center dot 2-41 center dot 6 %) than by the BMI cut-offs for each subgroup. Among pubertal girls, none of the BMI-based cut-offs indicated excellent agreement with body fat percentage, and kappa value of the WHO cut-offs (0 center dot 35 (95 % CI 0 center dot 29, 0 center dot 41)) was lower than the other two sets of BMI cut-offs (allP< 0 center dot 001). Conclusions: The IOTF cut-offs for Asian should be recommended for child obesity screening in urban China. Pubertal individuals need a more accurate indicator of obesity screening.