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Canadian Journal of Cardiology

The Problem of Diagnosing Pediatric Hypertension: Is Using Static Blood Pressure Cutoffs Instead of Blood Pressure Tables a Solution?

  • Blake Sandery
    Affiliations
    Division of Nephrology, Department of Pediatrics, University of British Columbia, BC Children’s Hospital, Vancouver, British Columbia, Canada
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  • Janis M. Dionne
    Correspondence
    Corresponding author: Dr Janis M. Dionne, Division of Nephrology, 4480 Oak Street, Vancouver, British Columbia V6H 3V4, Canada. Tel.: +1-604-875-2272; fax: +1-604-875-3649.
    Affiliations
    Division of Nephrology, Department of Pediatrics, University of British Columbia, BC Children’s Hospital, Vancouver, British Columbia, Canada
    Search for articles by this author
      The prevalence of hypertension in children ranges from 2% to 5%; however, children frequently go undiagnosed.
      • Sorof J.M.
      • Lai D.
      • Turner J.
      • Poffenbarger T.
      • Portman R.J.
      Overweight, ethnicity, and the prevalence of hypertension in school-aged children.
      • Moore W.E.
      • Stephens A.
      • Wilson T.
      • Wilson W.
      • Eichner J.E.
      Body mass index and blood pressure screening in a rural public school system: the Healthy Kids Project.
      • Hansen M.L.
      • Gunn P.W.
      • Kaelber D.C.
      Underdiagnosis of hypertension in children and adolescents.
      • Brady T.M.
      • Solomon B.S.
      • Neu A.M.
      • Siberry G.K.
      • Parekh R.S.
      Patient-, provider-, and clinic-level predictors of unrecognized elevated blood pressure in children.
      This is largely due to omission of blood pressure (BP) measurement or, when BP is measured, the failure to correctly recognise hypertensive values. Up to 70% of pediatric physicians measure BP only when risk factors for hypertension are present.
      • Bijlsma M.W.
      • Blufpand H.N.
      • Kaspers G.J.
      • Bokenkamp A.
      Why pediatricians fail to diagnose hypertension: a multicenter survey.
      In addition, when BP is measured and meets hypertensive criteria, up to 74% of patients are not diagnosed with hypertension.
      • Hansen M.L.
      • Gunn P.W.
      • Kaelber D.C.
      Underdiagnosis of hypertension in children and adolescents.
      This may be because pediatric physicians often do not compare measured BP with the diagnostic BP tables.
      • Bijlsma M.W.
      • Blufpand H.N.
      • Kaspers G.J.
      • Bokenkamp A.
      Why pediatricians fail to diagnose hypertension: a multicenter survey.
      These tables are cumbersome to use in clinical practice because they contain hundreds of values and also require that a child’s height is known. It has been suggested that the difficulty of using these tables contributes to the underdiagnosis of hypertension.
      • Hansen M.L.
      • Gunn P.W.
      • Kaelber D.C.
      Underdiagnosis of hypertension in children and adolescents.

      Defining the Problem … Is a Problem

      In recent decades, pediatric hypertension has been defined as a BP above the 95th percentile for age, sex, and height.
      National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents.
      ,
      • Nerenberg K.A.
      • Zarnke K.B.
      • Leung A.A.
      • et al.
      Hypertension Canada’s 2018 guidelines for diagnosis, risk assessment, prevention and treatment of hypertension in adults and children.
      Before 1996, BP norms were based only on age and sex, but it was noted that increasing height is associated with increasing BP in children, and as such height centile was added to the normative tables.
      National High Blood Pressure Education Program Working Group on Hypertension Control in Children and Adolescents. Update on the 1987 Task Force Report on High Blood Pressure in Children and Adolescents: a working group report from the National High Blood Pressure Education Program.
      Normative values were determined by examining the distribution of blood pressures among more than 60,000 children in the United States and have been updated over the years.
      National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents.
      ,
      National High Blood Pressure Education Program Working Group on Hypertension Control in Children and Adolescents. Update on the 1987 Task Force Report on High Blood Pressure in Children and Adolescents: a working group report from the National High Blood Pressure Education Program.
      ,
      • Flynn J.T.
      • Kaelber D.C.
      • Baker-Smith C.M.
      • Blowey D.
      • Carroll A.E.
      • Daniels S.R.
      • et al.
      Clinical practice guideline for screening and management of high blood pressure in children and adolescents.
      The 2017 Clinical Practice Guideline published by the American Academy of Pediatrics (AAP) updated the 4th Report normative values based on data obtained from only normal-weight children.
      • Flynn J.T.
      • Kaelber D.C.
      • Baker-Smith C.M.
      • Blowey D.
      • Carroll A.E.
      • Daniels S.R.
      • et al.
      Clinical practice guideline for screening and management of high blood pressure in children and adolescents.
      This was done because it is recognised that overweight and obese children often have higher BP than their normal-weight counterparts. The AAP guideline also recommends using threshold cutoffs of ≥ 120 systolic but < 80 diastolic to define elevated BP, and ≥ 130/80 to define hypertension in children 13 years of age and older to be consistent with the adult American Heart Association/American College of Cardiology BP recommendations.
      • Flynn J.T.
      • Kaelber D.C.
      • Baker-Smith C.M.
      • Blowey D.
      • Carroll A.E.
      • Daniels S.R.
      • et al.
      Clinical practice guideline for screening and management of high blood pressure in children and adolescents.
      Unfortunately, the childhood classifications are based on population norms and not on hypertensive target organ damage or trial outcome measures, which are needed to better refine the pediatric BP definitions.

      Evaluating Static Blood Pressure Cutoffs

      There is limited research examining whether use of static BP cutoffs link to cardiovascular outcomes in children. Static BP cutoffs are threshold values to define hypertension, used across multiple age groups, and not dependent on height. In this issue of the Canadian Journal of Cardiology, Yang et al. report on the ability of static BP cutoffs to determine elevated carotid intima-media thickness (cIMT) in an international pediatric cohort.
      • Yang L.
      • Whincup P.H.
      • López-Bermejo A.
      • et al.
      Use of static cutoffs of hypertension to determine high cIMT in children and adolescents: An international collaboration study.
      They compared the performance of these static cutoffs to the 95th percentile cutoffs outlined in the AAP 2017 Clinical Practice Guideline. For children aged 6-12 years, they used a BP of ≥ 110/70 mm Hg to define elevated blood pressure and BP ≥ 120/80 mm Hg to define hypertension. For adolescents aged 13 years or above, BP ≥ 120/< 80 mm Hg defined elevated BP and ≥ 130/80mm Hg was classified as hypertension.
      This was an international cross-sectional study including 4280 children aged 6-17 years.
      • Yang L.
      • Whincup P.H.
      • López-Bermejo A.
      • et al.
      Use of static cutoffs of hypertension to determine high cIMT in children and adolescents: An international collaboration study.
      The cohort included children from 6 countries—Brazil, China, Greece, Italy, Spain, and the United Kingdom. BP, cIMT, demographic data, and other cardiometabolic risk factors were recorded during 1 study visit, and there was no long-term follow-up. Yang et al. demonstrate that pediatric hypertension is associated with elevated cIMT. With the use of static cutoffs, hypertension was associated with elevated cIMT with an odds ratio of 1.65 (confidence interval [CI] 1.25-2.17) after adjusting for potential confounding factors. The AAP guidelines’ 95th percentile tables had a slightly lower odds ratio of 1.46 (CI 1.15-1.86) for risk of elevated cIMT. This study provides evidence that static threshold values have a correlation similar to complex BP tables for childhood hypertensive target organ damage, with the implication that the easier-to-use cutoff BP values may be equally useful clinically.
      Despite the study’s robustness, it has a few limitations. First, although multiple BP measurements were taken, they were all from a single clinic visit instead of the multiple occasions that are required to demonstrate persistence of elevated BP readings in children. cIMT was measured and recorded slightly differently at some of the study sites, and different devices were used for BP and cIMT across study sites. The multisite and international nature of their study makes the results of the paper more applicable to a wide pediatric population, yet the individual cohorts differed in their rates of hypertension and obesity. One must also keep in mind, as with all cross-sectional studies, that association does not prove causality. Yet it is rare in pediatric studies to be able to analyse data from such large cohorts. Another unique feature of this paper is that they used a static BP cutoff for younger children, whereas much of the previous literature has used static cutoffs only for adolescents. Having static cutoffs for younger children in addition to adolescents has the potential to increase the early recognition of BP abnormalities in children and has been included in Hypertension Canada’s 2020 guideline recommendations.
      • Rabi D.M.
      • McBrien K.A.
      • Sapir-Pichhadze R.
      • et al.
      Hypertension Canada’s 2020 comprehensive guidelines for the prevention, diagnosis, risk assessment, and treatment of hypertension in adults and children.
      There has been increasing literature to suggest that using static cutoffs to diagnose pediatric hypertension may be appropriate. In addition to the contribution by Yang et al., a couple of studies have examined how static BP cutoffs correlate with short-term end-organ damage in childhood.
      • Yang L.
      • Whincup P.H.
      • López-Bermejo A.
      • et al.
      Use of static cutoffs of hypertension to determine high cIMT in children and adolescents: An international collaboration study.
      ,
      • Zhao M.
      • Mill J.G.
      • Yan W.L.
      • et al.
      Static cut-points of hypertension and increased arterial stiffness in children and adolescents: the International Childhood Vascular Function Evaluation Consortium.
      ,
      • Khoury M.
      • Khoury P.R.
      • Dolan L.M.
      • Kimball T.R.
      • Urbina E.M.
      Clinical implications of the revised AAP pediatric hypertension guidelines.
      The International Childhood Vascular Function Evaluation Consortium examined the ability of static BP cutoffs to identify elevated pulse-wave velocity compared with the 2017 AAP guideline.
      • Zhao M.
      • Mill J.G.
      • Yan W.L.
      • et al.
      Static cut-points of hypertension and increased arterial stiffness in children and adolescents: the International Childhood Vascular Function Evaluation Consortium.
      The consortium used the same BP cutoffs as Yang et al. and found that hypertension was associated with increased arterial stiffness and that static BP cutoffs performed equally well to identify elevated pulse-wave velocity.
      • Zhao M.
      • Mill J.G.
      • Yan W.L.
      • et al.
      Static cut-points of hypertension and increased arterial stiffness in children and adolescents: the International Childhood Vascular Function Evaluation Consortium.
      In addition, Khoury et al. reported a comparison of the 4th Report percentile BP tables with the AAP BP classification to detect cardiovascular end-organ damage in adolescent overweight and diabetic patients.
      • Khoury M.
      • Khoury P.R.
      • Dolan L.M.
      • Kimball T.R.
      • Urbina E.M.
      Clinical implications of the revised AAP pediatric hypertension guidelines.
      They found that the AAP threshold BP definition had improved sensitivity to detect target-organ damage, including increased left ventricular mass, pulse-wave velocity, and cIMT.
      • Khoury M.
      • Khoury P.R.
      • Dolan L.M.
      • Kimball T.R.
      • Urbina E.M.
      Clinical implications of the revised AAP pediatric hypertension guidelines.
      There have also been a few studies examining the ability of childhood BP thresholds to predict adulthood cardiovascular outcomes. Xi et al. examined the ability of static BP cutoffs to predict adulthood increased cIMT, pulse-wave velocity, and left ventricular hypertrophy in the Bogalusa Heart Study cohort.
      • Xi B.
      • Zhang T.
      • Li S.
      • et al.
      Can pediatric hypertension criteria be simplified? A prediction analysis of subclinical cardiovascular outcomes from the Bogalusa Heart Study.
      In that cohort of 1225 children and adolescents with 27-year follow-up data, threshold BP cutoffs were able to predict composite adverse adult cardiovascular outcomes equally as well as the 4th Report percentile tables.
      • Xi B.
      • Zhang T.
      • Li S.
      • et al.
      Can pediatric hypertension criteria be simplified? A prediction analysis of subclinical cardiovascular outcomes from the Bogalusa Heart Study.
      Also analysing the Bogalusa Heart Study participants from childhood to adulthood, Du et al. reported on the risk of developing adulthood hypertension, left ventricular hypertrophy, or metabolic syndrome using the 4th Report compared with the AAP guidelines, including adolescent thresholds, to define pediatric hypertension.
      • Du T.
      • Fernandez C.
      • Barshop R.
      • et al.
      2017 pediatric hypertension guidelines improve prediction of adult cardiovascular outcomes.
      Of the 3940 study participants, 325 were reclassified to a higher BP category with the use of the AAP classification, and those patients were at higher risk of adverse adult cardiovascular outcomes than their normotensive counterparts.
      • Du T.
      • Fernandez C.
      • Barshop R.
      • et al.
      2017 pediatric hypertension guidelines improve prediction of adult cardiovascular outcomes.
      Using data from the Cardiovascular Risk in Young Finns Study, Aatola et al. examined the association of childhood BP by simplified cutoff thresholds and complex percentiles with the development of adulthood elevated pulse-wave velocity. They found that age-specific cutoffs were able to predict adult elevated pulse-wave velocity with accuracy similar to the percentile tables.
      • Aatola H.
      • Magnussen C.G.
      • Koivistoinen T.
      • et al.
      Simplified definitions of elevated pediatric blood pressure and high adult arterial stiffness.

      So, Do Cutoffs Make the Cut?

      Yang et al. have made a substantial contribution to the evidence that supports using static cutoffs for defining pediatric hypertension. We now have evidence that during childhood, threshold BP values are as associated with cardiovascular target-organ damage, including increased cIMT and pulse-wave velocity, as the complex BP tables.
      • Yang L.
      • Whincup P.H.
      • López-Bermejo A.
      • et al.
      Use of static cutoffs of hypertension to determine high cIMT in children and adolescents: An international collaboration study.
      ,
      • Zhao M.
      • Mill J.G.
      • Yan W.L.
      • et al.
      Static cut-points of hypertension and increased arterial stiffness in children and adolescents: the International Childhood Vascular Function Evaluation Consortium.
      There is also evidence that threshold BP values in childhood are equally predictive of adulthood cardiovascular disease, including hypertension, metabolic syndrome, left ventricular hypertrophy, increased cIMT, and arterial stiffness.
      • Xi B.
      • Zhang T.
      • Li S.
      • et al.
      Can pediatric hypertension criteria be simplified? A prediction analysis of subclinical cardiovascular outcomes from the Bogalusa Heart Study.
      • Du T.
      • Fernandez C.
      • Barshop R.
      • et al.
      2017 pediatric hypertension guidelines improve prediction of adult cardiovascular outcomes.
      • Aatola H.
      • Magnussen C.G.
      • Koivistoinen T.
      • et al.
      Simplified definitions of elevated pediatric blood pressure and high adult arterial stiffness.
      The strength of the evidence in the studies is likely the best we can expect because we are unlikely to ever have a study of long enough duration to link childhood BP values to adulthood cardiovascular mortality while controlling for all confounding factors over a lifetime.
      In fact, the most recent pediatric guidelines from the AAP, European Society of Hypertension, and Hypertension Canada all recommend using threshold BP values to define hypertension during childhood or adolescence.
      • Dionne J.M.
      Evidence gaps in the identification and treatment of hypertension in children.
      The trouble is that each guideline recommends slightly different BP cutoffs because the evidence to support the thresholds is new and evolving. Yet given the high rates of underdiagnosis of hypertension in children, it is time to start using threshold BP cutoffs in pediatrics. And while we use the cutoffs, we need to continue to evaluate the utility of the thresholds to identify hypertension, to predict target-organ damage, and to better determine the most accurate static values to use.

      Funding Sources

      The authors have no funding sources to declare.

      Disclosures

      The authors have no conflicts of interest to disclose.

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