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The Short and Long of Measuring Blood Pressures in Your Office
Abstract & Commentary
By Rahul Gupta, MD, MPH, FACP, Clinical Assistant Professor, West Virginia University School of Medicine, Charleston, WV. Dr. Gupta reports no financial relationship to this field of study
Synopsis: Compared with manual, automated blood pressure measurements significantly reduced the white coat response in otherwise healthy primary care patients with systolic hypertension while demonstrating a stronger correlation with awake ambulatory blood pressure readings.
Source: Myers MG, et al. Conventional versus automated measurement of blood pressure in primary care patients with systolic hypertension: Randomised parallel design controlled trial. BMJ 2011;342:d286.
Hypertension is the most common primary diagnosis in the united States. While about 30 percent of Americans are still unaware of being hypertensive, even in those diagnosed, the control rates (SBP < 140 mmHg and DBP < 90 mmHg) remain dismal at a mere 34 percent.1 Diagnosis of hypertension is critically dependent on accurate blood pressure (BP) measurement. Once diagnosed, in the majority of patients, controlling systolic hypertension has been considerably more difficult than controlling diastolic hypertension. Because adequate control of systolic BP is linked to a lower incidence of cardiovascular diseases such as myocardial infarction, heart failure, and stroke as well as renal diseases, it is vital to obtain accurate measurements during these individuals' outpatient office visits.2 Blood pressure readings taken in the physicians' office are often higher than home or ambulatory values. The level of BP measurement by using the 24-hour ambulatory blood pressure monitoring (ABPM) method correlates better than office measurements with target organ injury.3 Current guidelines recommend using ABPM for evaluation of white-coat hypertension as well as in certain other situations (to assess patients with apparent drug resistance, hypotensive symptoms with antihypertensive medications, episodic hypertension, and autonomic dysfunction).1 These guidelines also recommend using the auscultatory method of BP measurement for patients in the office as well as using home measurement devices for self measurement for patients. Interestingly, while fully automated sphygmomanometers are widely used in inpatient and outpatient settings across the United States and data suggests that such a use reduces or eliminates many of the factors contributing to imprecise BP readings in routine clinical practice, current guidelines do not recognize this use.4 Therefore, it is important to examine whether these automated office BP devices can improve on the quality and accuracy of the readings when compared with manual office devices as well as reduce the white coat response. The implications of such an evaluation may not only lead us to avoid unnecessary treatment in many individuals, but also may improve our understanding of the number of individuals whose BP may actually be under control when being treated.
In the study by Myers et al, a total of 555 study patients with systolic hypertension from 67 primary care practices in five cities across eastern Canada were enrolled. In this randomized controlled trial, practices were randomly allocated to either ongoing use of manual office blood pressure measurement (control group) or automated office blood pressure measurement (intervention group) using the BpTRU device. Using the 24-hour ABPM (with calculations for awake period) as the gold standard, office BP readings were compared before and after enrollment in the intervention and control groups. The basic difference in the two groups was that for the intervention group, a rest period was not needed before the first reading since the automated sphygmomanometer records BP by the oscillometric method and is designed to take an initial reading to verify that the cuff is properly positioned and five more readings are taken automatically at pre-specified intervals without the need for office staff being present. Main outcomes were measured by calculating the difference in systolic blood pressure between awake ambulatory blood pressure minus automated office blood pressure and awake ambulatory blood pressure minus manual office blood pressure.
The authors discovered that without changing their antihypertensive drug regimens, both the manual and automated groups showed a decrease in mean office BP between the most recently recorded pre-study routine office visit and the first visit to the physician after enrollment in the study. However, the decrease in BP for the intervention group was much greater. Results further demonstrated that the introduction of automated office BP measurements into routine primary care practice significantly reduced the white-coat response compared with the ongoing use of manual BP measurement. Additionally, the quality and accuracy of automated office readings were also considerably better when compared with manual office readings.
As a medical student, I was always taught that taking the time to manually recheck BP in a hypertensive patient was an incumbent part of good medical practice. Similarly, I have always emphasized this part of the physical examination to my students throughout the years. I will admit that it is difficult to give up this core tradition of practicing good primary care. However, once again, our personal biases and preferences must give way to evidence. Currently, this study adds to the mounting evidence suggesting that automated methods of BP measurement in primary care practices may not only be the way to obtain the most accurate measurements, but also be the way to avoid misdiagnosis and the resultant treatment which can often occur based solely on white-coat response. However, one must caution that the current study applies to compliant, otherwise healthy, primary care patients with systolic hypertension. Also, much of the benefit in ruling out white-coat hypertension in the current study's intervention group may be attributed to office staff leaving the patient room after the first reading was obtained since data have shown that such automated readings are similar to manual readings if the staff remains present in the room when the reading is taken.5 To me, there are two and a half issues to be considered here. One is accuracy for which the automated device seems to be superior. Second is the issue of providing the patient adequate rest and privacy in order to rule out a falsely elevated reading due to white-coat hypertension. Clearly, an automated device would more likely be able to achieve this goal. Lastly is the half issue of environmental concerns related to mercury content in manual blood pressure devices. I consider this half an issue since the risks of mercury spills from such devices in a medical setting has not yet been researched adequately. With the Joint National Committee on track to release its eighth report on prevention, detection, evaluation, and treatment of high blood pressure in spring 2012, it is critical that this body evaluates the developing data on automated BP measuring devices and provides relevant and timely guidance to physicians across the United States on this particular issue.
1. Chobanian AV, et al. The seventh report of the joint national committee on prevention, detection, evaluation, and treatment of high blood pressure: The JNC 7 report. JAMA 2003;289:2560-2572.
2. Neal B, et al. Effects of ACE inhibitors, calcium antagonists, and other blood-pressure-lowering drugs: Results of prospectively designed overviews of randomized trials. Blood Pressure Lowering Treatment Trialists' Collaboration. Lancet 2000;356:1955-64.
3. Prisant LM, et al. Clinical utility of ambulatory blood pressure monitoring in target organ complications and equipment choices. J Clin Pharmacol 1992;32:620-626.
4. Myers MG, Valdivieso M, Kiss A. Use of automated office blood pressure measurement to reduce the white coat response. J Hypertens 2009;27:280-286.
5. Vidt DG, et al. Taking blood pressure: Too important to trust to humans? Cleve Clin J Med 2010;77:683-688.