Applied Evidence

Avoiding missteps in BP measurement

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Making sure a patient is seated properly is just one way to ensure an accurate measurement. But steering clear of certain methods of measurement in particular patient populations is also important.



Blood pressure (BP) measurement is an essential component of the physical examination. The information gleaned through this simple but vitally important assessment provides a basis for critical decisions about diagnosis, prognosis, and therapy in a variety of health care settings. In the emergency department, it helps guide resuscitation efforts; in the intensive care unit, it helps to identify the deteriorating patient and guide vasopressor drug titration; in the ambulatory office setting, it helps to identify hypertension and the need for antihypertensive therapy.

In the office setting, inaccurate BP measurement can have profound effects. An overestimation by only 5 mm Hg would result in an erroneous diagnosis and unnecessary treatment of hypertension for about 27 million patients—entailing medication costs, potential adverse effects, and psychologic issues associated with this diagnosis. Conversely, underestimation by 5 mm Hg would miss about 21 million patients who actually have hypertension.1

Why accurate BP measurement matters so much

About 75 million adults in the United States have high BP,2 which costs the nation $46 billion annually in health care services, antihypertensive medications, and missed days of work.3 Among US adults ages 20 or older, the age-­adjusted prevalence of hypertension is estimated to be 34%, equivalent to 85.7 million adults.4

Defining hypertension. For the general population, the Eighth Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure ­(JNC-8) defines hypertension as a BP of 140/90 mm Hg or higher in adults younger than 60 and a BP of 150/90 mm Hg or higher in adults ages 60 or older. For patients with comorbid hypertension and diabetes, JNC-8 recommends pharmacologic treatment when BP is 140/90 mm Hg or higher, regardless of age.5

Accurate measurement of BP provides the rational basis for the management of hypertension, which in turn may decrease the risk for stroke, congestive heart failure, and other cardiovascular diseases. Several investigators6-8 have observed that differences in interarm systolic BP are associated with an increased risk for peripheral vascular disease, stroke, and other cardiovascular problems.

Multiple factors impact accuracy; some might surprise you

A number of factors may influence the accuracy of BP measurement in the office; these are generally classified as related to the patient, the observer, the technique or procedure, or the equipment used. A recent systematic review by Kallioinen et al9 empirically evaluated 29 potential sources of inaccuracy in the measurement of adult resting BP. Among them were

Patient-related: Recent meal or alcohol intake; recent caffeine or nicotine use; full bladder distention; cold exposure; white-coat effect. Given the simplicity of assessing for these influences, it is worthwhile for office staff to ask patients, prior to the recommended 3 to 5 minutes of rest before BP measurement, if they were rushing to make their appointment, need to void their bladder, or have consumed food or drink or used tobacco within the past 30 minutes.

Continue to: Observer-related...


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