Ambulatory Blood Pressure Monitoring in Children
Condition: Blood Pressure
Study type: Observational

Summary: 
      Ambulatory Blood Pressure Monitoring (ABPM) potentially offers a superior way to screen
      children for entry into antihypertensive trials, assuring that only those with true
      hypertension are enrolled.10 In addition, ABPM offers a better method to measure response to
      drug therapy.11-16 The ABPM device most commonly used in children (Spacelabs 90217 -
      Issaquah, Washington) has not been independently validated for use in this population. In
      1993, the British Hypertension Society (BHS) published a protocol for validating ABPM
      devices, including guidance for validation studies in children.17 More recently, the Working
      Group on Blood Pressure Monitoring of the European Society of Hypertension published
      revisions to these guidelines, but did not include children in this update.18 Unfortunately,
      the original BHS protocol suggests using a smaller group of children than the protocol
      outlines for adults. Since BP in children is more variable than in adults, this guidance is
      unlikely to be adequate for children. Hence, a large, stringent validation study needs to be
      conducted in a cohort of children using the methods similar to those used to validate the
      device in adults. Performance of the proposed validation study is needed to allow for the
      incorporation of ABPM into clinical trial designs of anti-hypertensives in children which
      will ultimately allow for more accurate identification of the hypertensive population and
      determination of response to therapy along with allowing for assessment of the chronobiologic
      profile of drug response over the dosing interval.9
    

Detailed description: 
      The diagnosis and treatment of hypertension remains a challenge in children and adolescents.1
      At present the diagnosis is made during medical encounters and depends on randomly applied
      auscultatory or oscillometric techniques.2 These measurements are influenced by multiple
      factors including diurnal variation, stress related effects (most notably the fact that the
      measurement is being performed in a physician's office or clinic), observer bias and the
      measurement process itself. In addition, these standard approaches provide little information
      regarding blood pressure and its variability in the patients' ambient environments.3,4 If and
      when a diagnosis of hypertension is made, lifestyle changes are often prescribed. In children
      and adolescents these recommendations meet with mixed results that often frustrate patients
      and families as well as caregivers. In most cases, where sufficient concern exists regarding
      the long-term health of end organs such as the heart, kidney, eye and brain, pharmacotherapy
      is recommended. Unfortunately, in these instances drugs are prescribed with little
      information to guide proper, age-related dosing or safety assessment. In studies conducted
      over the last decade more than half of the agents marketed for adults with hypertension
      failed to demonstrate sufficient activity in children and adolescents to meet regulatory
      requirements for labeling.5 While a significant amount of this apparent ambiguity appears to
      be related to the design of the studies assessing the efficacy and safety of these drugs in
      pediatric patients, perhaps a more significant problem in these studies was the determination
      of who is actually hypertensive in the first place. This supplement addresses this issue
      directly by introducing an innovative approach to the diagnosis of hypertension in children
      and adolescents. Once validated, ambulatory BP monitoring may be used to describe and model
      the chronobiological patterns of blood pressure among patients who have been recently
      diagnosed with hypertension using standard clinical criteria. This is a unique opportunity to
      assess treatment naïve patients and compare an innovative new approach to what is currently
      the gold standard.

      The current project is designed specifically to validate the use of ambulatory blood pressure
      monitoring (ABPM) in children and adolescents so that it may be used as a clinical tool for
      unambiguously making the diagnosis of hypertension in this patient population and then be
      used to guide pharmacotherapeutic intervention. The use of ABPM in children was first
      documented in 19916 and has subsequently been employed in children as young as 2 months of
      age. Despite its adjunctive use by more than 60% of pediatric nephrologists in North America,
      the device currently used in the majority of pediatric practices and research centers has
      never been validated in a pediatric population.

      In contrast, ABPM has become a world-wide standard for monitoring blood pressure in adults
      with suspected hypertension. It offers the advantages of multiple measurements of a dynamic
      process over a protracted period of time and permits the evaluation of diurnal patterns and
      nocturnal disease. It also offers distinct advantages in monitoring patients in their natural
      environment without observer bias while permitting objective assessment of apparent drug
      resistance and hypotensive events that might occur on therapy. Finally, ABPM measurements
      have been demonstrated to better correlate with cardiovascular morbidity and mortality than
      casual measurements.7 They also correlate with end organ damage in children.8 Performance of
      the proposed validation study is needed to allow for incorporation of ABPM into clinical
      trial designs related to the diagnosis and treatment of hypertension in children. ABPM will
      ultimately allow for more accurate determination of response to therapy and asses the
      chronobiologic profile of drug response over the dosing interval. Of the devices currently
      marketed, the Spacelabs 90217 offers the range of cuff sizes required by the pediatric
      population. Thus, it is this monitor that will be validated.
    

Intervention name(s): Spacelabs 90217
Intervention type(s): Device
Intervention description(s): Comparison of the two ways to measure blood pressure: using the ambulatory blood pressure device (Spacelabs 90217) versus the standard method of measuring blood pressure is done by using a stethoscope and a blood pressure cuff.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Children ages 6 to 18 years will be available for participation in this multicenter study.
        Subjects will be enrolled from community based general pediatric clinics and other
        well-child care areas within participating hospitals and clinics of the four participating
        sites. Enrollment will continue until a total of 85 subjects from each age category (6-<12
        years and ≥12- <18 years) successfully complete the study. In addition, enrollment will be
        dependent upon mean qualifying blood pressure and arm circumference such that a wide range
        of both are represented in each age group.