| Objectives(1) The first aim of this study was to compare the difference of BP by age, sex and height matching, and further identify the important influencing factors of BP among Chinese adolescents.(2) We compared the difference in the rates of hypertension among the adolescents aged12-17years in Changsha city, China by adopting a Chinese BP reference2010and the US BP reference in2004for children and adolescent, and further evaluate the accordance of the two different reference data in identifying hypertensive subject.(3) By calculating the blood pressure to height ratio index (BPHRI), we explore the predictive effect of BPHRI on child hypertension and further to simplify the pediatric BP percentile references using BP to height ratio index for screening for hypertension in Chinese children.Methods(1) A total of66481adolescent participants in the age of12-17years from49middle and high school in Changsha city were recruited by stratified cluster sampling, including33483girls and32998boys. BP, height, and body weight were measured.(2) A matching and a grouping technique were used to examine the role of sex, age, and height in BP levels, respectively.(3) Overweight and obesity were also defined according to sex-and age-specific Chinese reference data.(4)Height Z score of all participants were calculated by referring to both Chinese height reference and the US CDC2000growth chart. The definitions of prehypertension and hypertension followed the age-, gender-, and height-specific BP(the US reference only) percentile algorithm recommended by China and US National High Blood Pressure Education Program Working Group. Hypertension was defined as SBP/DBP>95th percentile. These US BP references were used as the gold standard..(5) The blood pressure to height ratio index was calculated according to the formula as, SBPHRI=SBP (mmHg)/height (cm) and DBPHRI=DBP (mmHg)/height (cm);(6) All data analysis were based on SPSS19.0.The statistical methods of t test, ANOVA, Chi-square test, multivariate linear regression analysis and Spearman’s correlation analysis were used for data process and analysis. The Kappa index was used to evaluate the agreement and accordance of two different reference data of identifying hypertensive subjects. Receiver operating characteristic curve analysis was performed to assess the performance of systolic BPHR (SBPHR) and diastolic BPHRI (DBPHRI) for screening for pediatric hypertension.ResultsPart1(1) The blood pressure level in both boys and girls were significantly increasing with age, and boys had a significantly higher SBP and DBP that of girls at same age.(P<0.001)(2) Boys had higher systolic BP (SBP) and diastolic BP (DBP) than girls after controlling for age and height.(3) BP increased with age after controlling for sex and height.(4)In each age group, both SBP and DBP increased alongside increasing height in boys and girls.(5) The results from multivariate linear regression analysis showed that the association between height and SBP0=0.24, P＜0.001)/DBP (β=0.18, P＜0.001) were much closer than that of age (β for SBP=0.15, β for DBP=0.12, both P＜0.001) and sex (β for SBP=0.21, β for DBP=0.13, both P＜0.001). For the multivariate linear regression model, R2=0.56, P＜0.001.Part2(1) The prevalence rate of hypertension in adolescent aged12-17years measured by Chinese and US reference were12.3%(14.3%for boys, and10.4%for girls) and4.3%(2.6%for boys, and6.0%for girls); hypertension rate defined by Chinese BP reference were significantly higher than the rate defined by US reference, and the rates of hypertension defined by both criterion significantly increased with age.(P＜0.001)(2) The average height of adolescents among12-13in girl and boy aged12-15years were obviously higher than other significant.(3) Out of all age groups, the hypertension rates defined by either BP reference were increased along with the up height percentiles. Further more, the hypertension rate gap between two definitions was enlarger gradually with the up-height percentiles;(4) There were only3.1%and86.5%of adolescents were diagnosis as hypertension by both BP references simultaneously.9.3%and5.0%of girls as well as8.2%and2.0%of boys were designated as systolic hypertension or (and) diastolic hypertension only by Chinese BP reference.(5) A weak accordance or agreement rate between two different BP reference in identifying systolic and diastolic hypertension in our research (Kappa=0.145for SBP and kappa=0.198for DBP, P<0.001)Part3(1) The mean of SBPHRI/DBPHRI was0.648/0.413in boys and0.638/0.416in girls. The difference of SBPHRI/DBPHRI between boys and girls in each age group were pretty minute, but still statistically significant (P＜0.001).(2) The correlation analysis showed that SBPHR was highly positively associated with SBP and DBPHR was highly positively associated with DBP. However, the correlation between SBPHRI/DBPHRI and age were extremely weak.(3) The optimal cutoffs of SBPHRI/DBPHRI for adolescent hypertension were0.76/0.48in boys and0.74/0.47in girls. Using SBPHRI to predict systolic hypertension, for boys, the AUC was0.996-0.997, the sensitivity was0.982-0.985, the specificity was0.967-0.978; for girls, the AUC was0.993-0.994, the sensitivity was0.947-0.973, the specificity was0.928-0.934. Using DBPHRI to predict diastolic hypertension, for boys, the AUC was0.987-0.995, the sensitivity was0.969-0.987, the specificity was0.925-0.974; for girls, the AUC curve was0.991-0.992, the sensitivity was0.950-0.966, the specificity was0.915-0.928. The PPV and NPV both SBPHRI and DBPHRI in prediction of children and adolescent hypertension ranged0.3-0.6and0.9-1.0in all age groups for boys and girls.Conclusion(1) Sex, age and height are all independent determinants for BP levels in Chinese adolescents. It is essential to incorporate these three factors for the establishment of the BP reference tables.(2)The accordance or agreement of two BP references in defining adolescent hypertension is not good; Systolic and diastolic hypertensive cutoff points in each age group were significant higher in the US BP reference than that of Chinese BP reference. Height, as well as age and sex, was considered in the US BP reference for children and adolescent, which insured higher diagnosis accuracy on pediatric hypertension than the Chinese BP reference does. Because not considering Height, the hypertension prevalences could probably be overestimated among those whose height were at extremely higher percentiles and be underestimated among those whose height were at extremely lower percentiles(3)BPHRI is simple and accurate for screening for hypertension with high sensitivity and specificity in Chinese adolescents aged12to17years. |
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