Ambulatory Blood Pressure Monitoring Should Be Used in the Primary Care Setting to Diagnose Hypertension

Hypertension is a progressive and chronic disease if left untreated. It results in vascular damage and is a major risk factor for cerebral vascular accidents and cognitive decline. It is a major risk factor for premature morbidity and mortality and accelerates the progression of kidney and heart disease. Treatment has been shown to improve outcomes. However, on the flipside, the inappropriate diagnosis of hypertension can result in exposure to unnecessary medications, physical restrictions, and increased costs. Therefore, accurate measurement of arterial pressure is necessary. Blood pressure is inherently variable and fluctuates with activity, stress, environment, and time of day. Twenty-four hour ambulatory blood pressure monitoring (ABPM) provides multiple daytime and nighttime readings within the patient’s regular environment. It has been found to be accurate and reproducible.1 ABPM remains an underutilized tool in the primary care clinic. It is a powerful diagnostic tool in the management of hypertension. Recently, the British National Health Service through the National Institute for Health and Clinical Excellence guidelines, recommended ABPM for all patients with the diagnosis of hypertension.2 Currently, no US guidelines or societies have endorsed its use as a sole diagnostic test. We argue new antihypertensive guidelines should recommend its use in the diagnosis and ongoing care of the hypertensive patient regardless of age. The strength of ABPM as a clinical tool is the numerous data points for interpretation. A standard report provides raw data and calculated 24-hour average blood pressures with corresponding pulse rate. ABPM uses a portable device that can be set up in the office before the end of the patient visit or is simple enough for most patients to set up at home. It consists of a noninvasive upper arm blood pressure cuff and remote storage device that is often worn by the patient on the belt line. Duration of monitoring is usually 24 hours but can be extended to >72 hours, thus improving diagnostic accuracy. Currently, the most common indication of ABPM is to evaluate for white coat hypertension or the reverse situation—so-called masked hypertension. These diagnoses are rarely made in the primary care setting because the validity of random office or home blood pressure measurements are not questioned. The use of ABPM in the primary care setting will increase diagnostic accuracy. Studies also support its utility to guide further diagnostic work-up because certain blood pressure patterns are commonly seen in secondary causes of hypertension.3 For example, the loss of nocturnal dipping may suggest obstructive sleep apnea or potential risk of chronic kidney disease.4,5 Finally, ABPM has prognostic value. It is the most predictive blood pressure monitoring method in determining cardiovascular risk in the setting of established hypertension.6 Unfortunately, primary hypertension does not only affect adults. Hypertension in children and adolescents is a growing health problem. The prevalence is 3.6%, and this does not include prehypertension, which has a prevalence of 3.4%.7 High blood pressure in childhood commonly leads to hypertension in adulthood. The use of ABPM in pediatric patients is more accurate in predicting end-organ damage.8 Furthermore, ABPM is especially helpful in evaluating children with chronic kidney disease or obesity.9,10 It can be used in infants, but most recommend limiting use to children aged ≥5 years with a height >120cm.11 One concern with ABPM from the perspective of evidence-based medicine is that currently there are no clear clinical outcomes to define ABPM hypertensive parameters. Experts have deemed that a 24-hour mean blood pressure >135/85mm Hg, a daytime mean >140/90mm Hg, or a nighttime mean >125/75 mmHg is diagnostic of hypertension in adults.12 Pediatrics has its own ABPM normative values, and the diagnosis is based on blood pressure load. If ≥25% of readings are above the 95th percentile for height, this is deemed hypertension.8 The lack of evidence-based parameters should not preclude ABPMs greater use in the primary care setting. Studies have shown the value of ABPM as a diagnostic and prognostic tool in the management of hypertension. Hypertension is the most common chronic disorder seen in primary care. Therefore, the primary care clinic is the place where ABPM should be prescribed and interpreted, rather than a specialty clinic. Although a number of concerns—initial cost, lack of reimbursement, specialized equipment, concern for additional staff training, and nonstandardized reports or interpretation—remain, these concerns are beginning to be minimized with more affordable machines and greater technology providing succinct data interpretation. The ability to monitor blood pressure outside the office is key to an accurate diagnosis and prognostication. Therefore, in the absence of ABPM, home blood pressure monitoring, which has been shown to also correlate with target-organ damage, can be used.13 However, home blood pressure monitoring requires a motivated patient (minimum of 12 readings over 3 days); a correct-sized blood pressure cuff must be purchased—often a nonreimbursed cost for the patient; and there is the loss of additional data provided by ABPM, including multiple readings, nocturnal blood pressures, and diurnal variations, which have further prognostic value. It is now apparent that many blood pressure measurements in the office are imprecise, and proper technique is difficult in a typical outpatient clinic. In the pediatric population, white coat hypertension has an incidence of 40%;14 masked hypertension has a prevalence of 9%.15 In adults, multiple factors, such as talking, having a distended bladder, or sitting without back or arm support, affect blood pressure levels.16 Furthermore, the cost savings of accurately diagnosing hypertension cannot be overstated. In 2010, hypertension care, treatment, and missed work days had an estimated cost of $76.6 billion.17 ABPM has been shown to be cost effective in pediatric (estimated savings of $2.4 million per 1,000 patients) and adult patients (estimated savings of $16 million over 4–5 years).18,19 We believe the soon-expected Eighth Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC 8/JNC 2013) should be so “nice” as to recommend ABPM for the health of patients with concern for hypertension. The authors declared no conflict of interest.