[Waist circumference reference values in Beijing versus the national values in detecting cardiovascular risk factors in 7-18 years old children].

OBJECTIVE: To compare the optimal references of waist circumference (WC) between Beijing and China in detecting cardiovascular risk factors in school-age children.

METHODS: Percentile curves for WC were drawn by sex using LMS method based on 21 787 children and adolescents aged 7 - 18 from Beijing Child and Adolescent Metabolic Syndrome Study. The 75(th) and the 90(th) percentiles by age and by gender of WC percentile curves were chosen as the optimal WC reference for 3 - 18 years old children and adolescents in Beijing. The sensitivities (Se) and specificities (Sp) were compared between Beijing and China WC references based on the evaluation of cardiovascular risk factors including hypertension, dyslipidemia, impaired fasting glucose and non-alcoholic fatty liver disease (NAFLD) in the test population being composed of 4927 school children aged 7 - 18 years. The predictive values for those cardiovascular risk factors were compared between the two optimal thresholds through comparison of the odds ratio (OR) in regression analysis.

RESULTS: The optimal reference for Beijing children and adolescents aged 3 - 18 years ranged from 51.8 to 78.2 cm for the 75(th) percentile in boys and 50.8 to 72.1 cm in girls, and the 90(th) percentile increased from 54.0 to 86.0 cm in boys and 53.3 to 77.3 cm in girls. The Ses of Beijing and China WC references in detecting hypertension were 0.74 and 0.82 in boys and 0.68 and 0.73 in girls; the Ses were 0.69 and 0.80 in detecting low-high density lipoprotein in boys and 0.64 and 0.71 in girls; and they were 0.98 and 1.00 in boys and both were 0.93 in girls for NAFLD. The Sps of Beijing and China WC references in screening hypertension were 0.62 and 0.53 in boys and 0.68 and 0.63 in girls, respectively. In predicting low-high density lipoprotein, the Sps were 0.59 and 0.50 in boys and 0.66 and 0.61 in girls, the Sps were 0.60 and 0.50 in boys and 0.56 and 0.51 in girls for predicting NAFLD. After adjustment for age and gender, ORs and their 95% credibility intervals (CI) of the 90(th) WC percentiles of Beijing and China school children were 6.3 (5.2 - 7.7) and 6.0 (4.9 - 7.4) in predicting hypertension. Both predictive ORs and their 95%CIs were 1.3 (1.1 - 1.5) in predicting impaired fasting glucose and the both were 2.9 (2.5 - 3.4) for dyslipidemia. In predicting NAFLD the ORs and their 95%CIs were 49.1 (12.0 - 201.6) and 69.8 (9.7 - 504.2) for Beijing and China WC optimal references, separately.

CONCLUSION: Compared with Chinese WC reference, WC reference of Beijing had high Sps in screening cardiovascular risk factors in 7 - 18 years old children. The predictive values were not significant different between Beijing and China WC references for almost all cardiovascular risk factors except NAFLD. The WC reference in Beijing was more practical and handy for reference in Beijing and other north developed metropolises.