Stability of Blood Pressure and Diagnosis of Hypertension in Childhood

Longitudinal tracking studies as well as multiple long-term cohort studies have demonstrated that blood pressure (BP) in childhood tracks into adulthood and that individuals with high BP levels in childhood are more likely to develop intermediate markers of cardiovascular disease by adulthood than those with normal BP.¹  What is less well understood is what happens to childhood BP levels over shorter periods of time: weeks, months, or just a few years? This question is relevant to making a diagnosis of hypertension because the 2017 American Academy of Pediatrics (AAP) Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents (CPG) recommends repeat BP measurements over a period of weeks to months (depending on how high the BP category) before making a diagnosis of hypertension.²  This recommendation is based on the known lability of childhood BP over short time periods, a point that was established by Ogborn and Crocker over 30 years ago.³ 

In their study reported in this issue of Pediatrics, Kaelber et al⁴  provide some new insights into this question. Using electronic health record data, they retrospectively examined BP measurements from primary care practices to ascertain the natural history of abnormal childhood BP measurements over 2 consecutive 36-month periods. They found that only 30% of children with BP readings in the elevated category diagnosed over the first 36 months continued to have abnormal BP readings during the second 36 months and that 48% of children meeting criteria for stage 1 hypertension during the first 36 months continued to demonstrate abnormal BP during the second 36 months. An additional finding only briefly mentioned by the authors was that 12% of children with elevated BP progressed to a higher BP category, and 5% of children with stage 1 hypertension progressed to stage 2 hypertension in the second 36 months. Similar findings have been seen in analyses of school BP screening data from the Houston Pediatric and Adolescent Hypertension Program,⁵  as well as from analyses of the National High Blood Pressure Education Program childhood hypertension database,⁶  which highlights the need for ongoing follow-up of abnormal BP readings in a child or adolescent. Finally, they found that many children with initially elevated or hypertensive BP readings failed to receive follow-up BP readings as recommended in the AAP CPG.

As noted by the authors, these data have notable limitations, especially reliance on BP readings obtained across a wide variety of clinical sites that would no doubt have used a variety of BP measurement devices and protocols. The standardized BP measurement protocol outlined in the AAP CPG,²  specifically the use of carefully obtained auscultatory BP readings, is designed to minimize variability and, if followed, should result in more reliable data. Standardized BP measurement has also been recommended for diagnosis of hypertension in adults⁷  and has been successfully used in research studies involving children.^8,9  Reliance on office BP measurements alone may also be problematic because some of the children diagnosed with elevated BP and hypertension may have actually had white coat hypertension if 24-hour ambulatory BP monitoring had been performed to confirm the diagnosis.² 

The issue of failure to follow guidelines in the diagnosis of childhood hypertension has been described by multiple studies dating back to Dr Kaelber’s 2007 study demonstrating that only 22% of children who met the criteria from the 2004 National High Blood Pressure Education Program Fourth Report¹⁰  for diagnosis of hypertension were actually diagnosed as having hypertension.¹¹  Fast-forward to 2020, three years after publication of the AAP CPG; we continue to see papers outlining missed or delayed subspecialty referral for evaluation of hypertension¹²  and failure to perform recommended BP screening in young children with underlying conditions known to predispose to the development of hypertension.¹³  Unfortunately, failure to adhere to guidelines is not unique to BP measurement and diagnosis of hypertension; even height and weight are frequently not documented at preventive and well-child visits.¹⁴  The current study certainly shines additional light on this problem but does not provide new insights on how to improve guideline adherence.

In this study, Kaelber et al⁴  confirm that BP in childhood can vary over time; from a prevention standpoint, the fact that some children’s BP falls over time is less important than the fact that a notable percentage progress to higher BP categories. Repeated measures of BP over time by using a standard technique are needed to identify children who may be at risk for developing adult cardiovascular disease.

AAP

American Academy of Pediatrics

BP

blood pressure

CPG

Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents