Researchers at Johns Hopkins Medicine have determined that the positioning of a patient’s arm during blood pressure (BP) screenings can significantly inflate test results, potentially resulting in misdiagnosis of hypertension.
A study led by Johns Hopkins Medicine researchers has found that the way a patient’s arm is positioned during blood pressure screenings can greatly exaggerate test results and might lead to incorrect diagnoses of high blood pressure.
A report on this study, due to be published on October 7 in JAMA Internal Medicine, explored the impact of three different arm positions: one supported on a desk, one on a lap, and one hanging unsupported at the side of the patient. The researchers discovered that when the arm is on the lap, systolic pressure (the top number in a BP reading) was overestimated by nearly 4 mmHg, while an unsupported arm at the side resulted in an overestimation of nearly 7 mmHg.
According to Tammy Brady, M.D., Ph.D., who is the vice chair for clinical research in the Department of Pediatrics at the Johns Hopkins University School of Medicine, and the study’s senior author, the findings highlight that arm position significantly influences the accuracy of blood pressure measurements. The study emphasizes the need to follow clinical guidelines that recommend firm support for the arm on a desk or table during BP assessments.
The American Heart Association indicates that almost half of adults in the U.S. experience elevated blood pressure, a condition defined when the force of blood against the walls of blood vessels exceeds normal levels, which is typically around 120/80 mmHg. If left untreated, high blood pressure raises the risk of severe cardiovascular issues like stroke and heart attacks. Since hypertension often presents with minimal or no symptoms, consistent screenings during routine checkups are vital for managing the condition. Most patients can keep their BP in check through lifestyle alterations—such as losing weight, eating a healthy diet, and engaging in regular exercise—along with various medications available for treatment.
The latest guidelines from the American Heart Association stress several important factors to ensure accurate measurements, including selecting the correct cuff size, providing proper back support, keeping feet flat on the floor with legs uncrossed, and positioning the arm so that the middle of the BP cuff aligns with heart level on a desk or table.
Despite these recommendations, the researchers noted that blood pressure is often measured with patients seated on exam tables where arm support is poorly managed or nonexistent. In certain instances, a clinician may hold the patient’s arm, or the patient themselves may keep an arm in their lap. In this recent Johns Hopkins study, the research involved 133 adult participants (78% Black, 52% female), recruited between August 9, 2022, and June 1, 2023. The participants, aged 18 to 80, were randomly assigned to one of six groups that varied based on the order of the three arm positions. Measurements were taken in a single visit throughout the day. Before BP measurements, all participants emptied their bladders and walked for two minutes to emulate a typical clinic setting where patients arrive for screenings. Then, they rested seated for five minutes, ensuring their backs and feet were supported. Each participant wore an upper arm BP cuff tailored to their arm size, with three sets of measurements conducted using a digital BP device, spaced 30 seconds apart.
Once all sets of three measurements were taken, the cuff was removed, and participants walked and rested again before undergoing a fourth set of measurements while their arm was supported on a desk, allowing researchers to control for known variations in BP readings. All assessments were carried out in a quiet, private environment, and participants were instructed to minimize conversations and phone usage during the process.
The study found that BP measurements taken with commonly used arm positions—an arm on the lap or hanging unsupported at the side—were significantly elevated compared to those recorded with the arm properly supported on a desk, which is the recommended position. Specifically, supporting the arm on the lap led to an overestimated systolic BP of 3.9 mmHg and a diastolic BP (the lower number) of 4.0 mmHg. On the other hand, an unsupported arm at the side resulted in an overestimation of systolic pressure by 6.5 mmHg and diastolic by 4.4 mmHg. “If blood pressure is consistently measured with an unsupported arm, yielding an overestimation of 6.5 mmHg, this could indicate a crucial difference between a systolic reading of 123 and 130, or 133 and 140—which falls into the category of stage 2 hypertension,” remarks Sherry Liu, M.H.S., an epidemiology research coordinator involved in the study.
Researchers caution that their findings may primarily apply to BP measurements taken with automated devices and may not extend to readings obtained with other instruments. However, Brady asserts that clinicians should pay closer attention to best practice guidelines, and patients should “advocate for themselves when it comes to their BP measurements in clinical settings and at home.”
Alongside Brady and Liu, the other authors from Johns Hopkins include Di Zhao, Ahmed Sabit, Chathurangi Pathiravasan, Junichi Ishigami, Jeanne Charleston, Edgar Miller III, Kunihiro Matsushita, and Lawrence Appel.
This study received support from Resolve to Save Lives, which is funded by Bloomberg Philanthropies, the Bill and Melinda Gates Foundation, and Gates Philanthropy Partners, with support from the Chan Zuckerberg Foundation.
