Performance Of Dichotomous And Continuous Pediatric Metabolic Syndrome Definitions In Identifying Early Vascular Damage

BackgroundRecently,with the rapid socio-economic development and the prevailing of unhealthy lifestyles,childhood obesity has been an important public health issue.Pediatric obesity is associated with various metabolic disorders,such as elevated blood pressure,impaired glucose metabolism and dyslipidemia.It is called metabolic syndrome(MetS)if more than three risk factors are aggregated together.Data from the 2010 China Noncommunicable Disease Surveillance showed that the overall prevalence of MetS in Chinese adults aged 18 years and older was 33.9%.Data from 2010?2012 China Health and Nutrition Survey showed that the prevalence of MetS among Chinese children aged 10?17years was 2.4%.Prospective studies showed that childhood MetS increased the risk of cardiovascular disease and type 2 diabetes mellitus in the future.Therefore,it is important to screen childhood MetS and then make effective interventions,in order to reduce cardiovascular diseases burden in our country.However,there is no consensus on the definition of pediatric MetS.And more than 40 diagnostic criteria of MetS in children have been proposed.Differences in the components and cut-offs of the various criteria make a direct comparison between studies impossible.Therefore,it is important to harmonize and standardize the diagnostic criteria of MetS in children and adolescents.Recent studies showed that the traditional dichotomous MetS had poor stability,and several researchers have proposed the definition of continuous MetS(cMetS)scores.Compared with dichotomous MetS,cMetS scores may have better ability to predict cardiovascular damages.Several studies from western countries have shown that cMetS scores performed better in predicting early vascular damage than dichotomous MetS.However,some reported that cMetS scores did not increase the predictive utility compared with a dichotomous definition of MetS.Studies on the relationship between MetS and target organ damage in Chinese pediatric population are rarely reported.Objectives(1)To examine the performance of five commonly used dichotomous MetS criteria,including the China criteria,the American National Cholesterol Education Program(NCEP)criteria,the International Diabetes Federation(IDF)criteria,the American Heart Association(AHA)criteria,and the World Health Organization(WHO)criteria,in identifying early vascular damage.(2)To examine the utility of cMetS scores vs.the dichotomous MetS definition in identifying early vascular damage.Subjects and methodsThis study was based on the "Children Cardiovascular Health Cohort" project.This project was conducted in a school in Zibo city between November 2017 and January 2018 to collect baseline data.A total of 1416 students aged 6-11 years were included in the present study.Students were voluntary to participate in the survey and we obtained informed consent from their parents.All eligible participants underwent physical examinations,including anthropometric examinations,biochemical tests,and ultrasonography examinations.A medical check-up questionnaire was used to collect basic information,such age and sex.Anthropometric examinations were conducted to obtain information on weight,height,waist circumference,and blood pressure of the study subjects.Blood biochemical analysis was performed to measure fasting plasma glucose,triglycerides,total cholesterol,high-density lipoprotein cholesterol,and low-density lipoprotein cholesterol.Ultrasonography examinations were conducted to assess carotid intima-media thickness(cIMT)of the subjects.Statistical analysis:SAS software version 9.3 was used for data analysis,SPSS software version 21.0 was used to draw receiver operating characteristics(ROC)curve,and Graphpad Prism software version 7.0 was used to draw other statistical graphs.For continuous variables,t test,or covariance analysis or multiple linear regression analysis was performed to examine differences between groups.Chi-square test was used to compare differences in categorical variables between groups.Kappa value was calculated as a measure of agreement between two MetS criteria.Logistic regression analysis was performed to calculate the odds ratios(ORs)and 95%confidence intervals(CIs)of early vascular damage for children with MetS vs.non-MetS controls.ROC analysis was used to compare the performance of various MetS criteria in screening early vascular damage.cMetS scores were calculated by using standardized Z-scores and principal components analysis.ROC analysis and net reclassification improvement(NRI)analysis were utilized to evaluate the efficacy of cMetS scores in detecting early vascular damage.P<0.05 indicates statistical significance.Results1 Detection rates of MetS in children according to five dichotomous MetS criteria and their agreementAccording to the China criteria,NCEP criteria,IDF criteria,AHA criteria and WHO criteria,the detection rates of MetS in children aged 6-11 years were 5.5%,5.4%,1.0%,8.8%,and 1.0%,respectively.There was relatively high agreement between NCEP criteria and AHA criteria,and between NCEP criteria and China criteria,with the kappa values being 0.74(95%CI:0.67-0.81)and 0.63(95%CI:0.54?0.72),respectively.However,the agreement between other criteria was poor,with the kappa values ranging from 0.19 to 0.59.2 Performance of five dichotomous MetS criteria in identifying early vascular damageBased on any of the five MetS criteria,compared with children without MetS,those diagnosed with MetS were at increased risk of early vascular damage.And the detection rates of early vascular damage increased with the number of metabolic components.But the ROC analysis showed that the sensitivity and positive predictive value of dichotomous MetS criteria in identifying early vascular damage were both very low.Areas under the ROC curves of the five dichotomous MetS criteria were also very low,with the largest being 0.65(95%CI:0.61-0.69)(AHA criteria).For IDF criteria and WHO criteria,areas under the ROC curves were only 0.52(95%CI:0.50?0.54)and 0.53(95%CI:0.51-0.55),respectively.Therefore,the five MetS criteria did not perform well in identifying early vascular damage.3 Performance of cMetS scores in identifying early vascular damageAccording to the quartiles of cMetS Z scores,detection rates of early vascular damage increased gradually with the percentile levels of cMetS Z scores.cMetS Z score was a risk factor for early vascular damage,with the OR value being 1.59(95%CI:1.48-1.70).ROC analysis showed that the performance of cMetS Z scores in identifying early vascular damage was good,with the area under the curve being 0.83(95%CI:0.81-0.85).NRI analysis showed that compared with the dichotomous MetS,the accuracy of the cMetS Z scores in the diagnosis of early vascular damage was improved greatly(P<0.001).The cMetS PC scores presented similar results.Conclusions(1)The detection rates of MetS varied largely according to the five dichotomous pediatric MetS criteria,and the agreement was poor between most of the criteria.(2)All the five dichotomous pediatric MetS criteria performed poor in identifying early vascular damage.(3)cMetS scores performed better in identifying early vascular damage than the dichotomous pediatric MetS.