The validation of the classification criterion of waist and waist-to-height ratio for cardiometabolic risk factors in Chinese school-age children

Objective To restudy and identify the cutoffs for waist circumference and waist-to-height ratio that indicate increased risk of cardiovascular risk factors and their clustering that would be consistent with central adiposity in Chinese school-age children.Methods The author of this paper had brought forward 80th percentile of waist circumference by age and gender and waist-to-height ratio equal to 0.46 as the primary cutoffs of school-age children and adolescents central adiposity in the BCAMS study,which was a cross-sectional representative population based survey on Metabolic Syndrome for Children and Adolescents in Beijing.But the cardiovascular risk factors results were based on the finger-stick capillary test in that study.This time a total of 3 525 school-age children aged 6-18 years were recruited from the BCAMS study.1 454 schoolchildren aged 7-18 years were recruited from 8 schools in district of Haidian in Beijing.Data of anthropometric measures including weight,height,waist circumference and blood pressure were collected.Venous blood samples were obtained after a 12-hour fast,and the levels of fasting plasma glucose(FPG),triglyceride(TG),total cholesterol(TC),low density lipoprotein(LDL-C) and high density lipoprotein-cholesterol(HDL-C) were measured.In this study high blood pressure(HBP) was defined as systolic blood pressure(SBP) and/or diastolic blood pressure(DBP) ≥95 th percentile for age and gender of schoolchildren in Beijing in 2004.Impaired fasting glucose(IFG) was diagnosed according to updated ADA standard of USA(2005,FG≥5.6 mmol·L-1),blood levels of TG≥1.7 mmol·L-1,blood levels of TC≥5.2 mmol·L-1,HDL-C≤1.03 mmol·L-1 were defined as raised TG,raised TC and Low HDL-C,respectively.For the 1 454 recruited children in Haidian,liver were tested by ultrasonographic,and abnormal hepatic sonograms were diagnosed additionally.Elevated glutamate-pyruvate transaminase was diagnosed by ALT≥40.0 U·L-1 and elevated glutamic-oxalacetic transaminase was determined by AST≥45.0 U·L-1.Nonalcoholic fatty liver was diagnosed according to the diagnostic criteria of nonalcoholic fatty liver disease recommended by the Fatty Liver and Alcoholic Liver Disease Study Group of Chinese Liver Disease Association.70 th,75 th,80 th,85 th,90 th and 95 th percentiles by gender and age for WC,WHtR equal to 0.42,0.44,0.46,0.48,0.50 and 0.52 were selected as temporary criterions based on primary screening cutoffs brought forward in the last paper of the author.Statistic methods included the followings,measurement data were expressed by mean and standard deviation and analyzed with independent sample t-test,categorical data were compared with chi-square analyze,analysis of covariance adjusted by gender,age and puberty status was used to compare the level of cardiovascularity in stratification,and classical screening study.A probability level of P 0.05 was used to indicate statistical significance.Results Mean BMI,systolic blood pressure,diastolic blood pressure,triglyceride and total cholesterol levels were incrementally higher and mean HDL-cholesterol values were incrementally lower with each unit increase in waist circumference and waist-to-height ratio.And the abnormal rates of the cardiovascular risk factors and their clustering increased with WC and WHtR.Both the points at which sensitivity and specificity were equally perfect at sex,age-specified 85th percentile of waist circumference and a waist-to-height ratio of 0.48 optimal cutoffs.At those points positive predictive value and negative predictive value were all optimal.Conclusions Cutoffs of waist circumference at 85th percentile by age and gender and waist-to-height ratio equal to 0.48 are needed in the identification of Chinese school-age children and adolescents at high risk of cardiovascular risk factors and their clustering.