Researchers at Johns Hopkins Medicine have found that the way a patient’s arm is positioned during blood pressure (BP) screenings can significantly affect the results, potentially leading to an overestimation and misdiagnosis of hypertension.
The study, published in JAMA Internal Medicine, highlights the importance of proper arm support when measuring BP, as commonly used positions can produce inaccurate readings.
In the study, the team examined three different arm positions: an arm supported on a desk, an arm supported on the lap, and an unsupported arm hanging at the patient’s side.
They discovered that these alternative positions overestimated blood pressure levels, with the unsupported arm showing the most significant effect.
An unsupported arm led to an overestimation of systolic pressure (the top number in a BP reading) by nearly 7 mmHg, while lap support overestimated systolic pressure by almost 4 mmHg.
Dr. Tammy Brady, senior author of the study and medical director of the pediatric hypertension program at Johns Hopkins Children’s Center, emphasized the impact of this finding. “Arm position makes a huge difference in getting an accurate blood pressure measurement,” she said.
The researchers stress the need for clinicians to follow the proper guidelines, which recommend that the arm should be supported on a desk or table at mid-heart level for the most accurate results.
Hypertension, or high blood pressure, is a common condition where the force of blood flowing through the arteries is consistently too high. Left untreated, it can lead to serious health problems, including stroke and heart attack.
According to the American Heart Association, nearly half of adults in the U.S. have elevated blood pressure, making accurate screening essential for diagnosis and management.
In the study, 133 adult participants between the ages of 18 and 80 were randomly assigned to six different groups, each with varying arm positions.
Researchers took multiple BP measurements during a single visit, ensuring that participants followed a routine similar to a typical doctor’s visit—emptying their bladders, walking briefly, and resting before the readings.
The researchers found that improper arm positioning consistently resulted in higher blood pressure readings.
For instance, when the arm was supported on the lap, systolic BP was overestimated by 3.9 mmHg and diastolic BP (the bottom number, which measures pressure between heartbeats) by 4.0 mmHg. When the arm was left hanging unsupported, systolic BP was overestimated by 6.5 mmHg and diastolic BP by 4.4 mmHg.
To put this into perspective, a systolic difference of 6.5 mmHg could be the difference between a BP reading of 123 and 130 mmHg. Since a systolic BP of 130 mmHg is the threshold for stage 1 hypertension, inaccurate measurements could result in misdiagnosis and unnecessary treatment.
Sherry Liu, a study author and research coordinator at Johns Hopkins, noted the significance of these findings. “Consistently measuring BP with an unsupported arm can lead to overestimations that push readings into the range of hypertension,” she said.
This is especially problematic because hypertension is often diagnosed without obvious symptoms, making early and accurate screening crucial.
While the study focused on automated BP devices, the researchers acknowledge that their findings may not apply to other types of BP measurement tools. Nevertheless, they recommend that clinicians strictly adhere to the clinical guidelines for BP measurement, which include proper arm support.
Dr. Brady also urged patients to be proactive during checkups, suggesting that they ask for proper arm support during BP screenings and follow best practices when checking their blood pressure at home.
According to the American Heart Association’s guidelines, normal BP is considered to be below 120/80 mmHg, with elevated BP defined as between 120-129/80 mmHg. Hypertension is diagnosed at 130/80 mmHg or higher.
Factors like stress, diet, caffeine, and smoking can affect BP readings, making it critical to measure BP under consistent conditions for the most accurate results.
This study underscores the importance of following clinical guidelines to ensure BP readings are accurate. Proper arm support is not just a small detail—it can make the difference between a correct diagnosis and a misdiagnosis, potentially altering a patient’s treatment plan and overall health management.
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The research findings can be found in JAMA Internal Medicine.
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