Wrong sized blood pressure cuff tied to inaccurate readings, possible misdiagnoses

Jun 20, 2024

Healio Interviews

Healio Interviews

Using the wrong size arm cuff when performing a standard BP measurement can lead to “strikingly inaccurate” measurements that may lead to a hypertension misdiagnosis, according to data from a randomized crossover trial.

In a recent study with 195 adults with a wide range of mid-arm circumferences, the use of a regular BP cuff resulted in a 3.6 mm Hg lower systolic BP reading among people who required a small BP cuff, according to Tammy M. Brady, MD, PhD, vice chair for clinical research in pediatrics and associate professor of pediatrics in the division of pediatric nephrology and medical director of the Pediatric Hypertension Program at Johns Hopkins University School of Medicine.

In contrast, among people who required a large or extra-large BP cuff, use of a regular cuff resulted in 4.8 mm Hg higher systolic BP reading for those requiring a large cuff and a 19.5 mm Hg higher systolic BP reading for those requiring an extra-large cuff. The data suggest a renewed emphasis on individualized BP cuff selection is warranted, particularly for people with larger arm sizes, Brady said.

Healio spoke with Brady about the consequences of “mis-cuffing” when measuring BP, how to find a validated BP device and cuff, and the importance of spreading the message on cuff size to patients and anyone who measures BP.

Brady and colleagues’ research was recently published in JAMA Internal Medicine.

Healio: What led you and your colleagues to conduct research on BP device cuff size?

Brady: I see many children who are referred for elevated BP, and many of the children I see for evaluation had strikingly lower BPs when I measured them manually with a cuff selected based on a measurement of their arm circumference. Many of those families would share that they had never seen a cuff that size used on their child. My colleagues who worked with the nonprofit Resolve to Save Lives were working in under-resourced settings where lots of BP screening efforts are being implemented. Many of those sites have portable devices with just one arm cuff. Even when there are other cuff sizes available, they are not readily available, so many people are screened with the adult cuff that comes with the device. We wanted to know how important individualized cuff size selection is for detecting hypertension. Our hope was maybe we could simplify things. As it turns out, not only is cuff size important, but it is very important.

Healio: Can you discuss the study design?

Brady: We wanted to approach the cuff size issue two different ways. One, we wanted to assess the impact of cuff size on BP measurement accuracy when using the regular adult size cuff for allcomers. We presented those results at the American Heart Association’s Epidemiology, Prevention, Lifestyle & Cardiometabolic Scientific Sessions meeting. Those data showed if you use a regular adult cuff for all-comers, a person with an arm circumference that requires a large or an extra-large size adult cuff — which is the more common scenario in the U.S. — the BPs the device would provide were strikingly higher than what the true BP would be. Measurements were anywhere from 5 to 20 mm Hg higher than the person’s actual BP. If the person required a smaller cuff size, the adult size cuff would underestimate their BP by an average of 3.5 mm Hg.

Our other aim was to see what happens if you use a large size cuff when an extra-large size cuff should have been used instead, and assess the impact of that type of mis-cuffing. That also showed inaccuracies in BP measurements.

Healio: What are the consequences of an incorrect BP reading due to wrong cuff size?

Brady: The concern is there will be missed diagnoses of hypertension or overdiagnoses of hypertension, both of which have a multitude of clinical consequences. You could overtreat; you could undertreat. With overtreatment comes concerns that you may induce hypotensive symptoms, but there is also missed work, stress and unnecessary testing that can occur.

Healio: What do clinicians need to know?

Brady: A lot of physicians and nurses recognize the importance of using an appropriately sized BP cuff. The take home message is that not only do the providers need to know, but the people who are actually measuring the BP also need to know about appropriate cuff size selection. That filters down to the medical assistants, some pharmacists and the patients themselves. Many people try to do the right thing and purchase a BP device from a pharmacy to monitor their BP at home, not recognizing that they need to make sure that the cuff that comes with the device is the correct size for their arm.

Additionally, providers who are presented with a BP measurement, say, from the triage setting, need to inquire about what cuff size was used when that measurement was obtained.

Healio: How does someone assess a BP device for accuracy?

Brady: There are two key answers. First, a patient should know that they must purchase a device that has been tested for accuracy. I am a co-chair of the American Medical Association’s validated device listing independent review committee. We work to identify devices that have undergone appropriate validation testing. On validateBP.org, there is a listing of devices for sale in the U.S. that have been validated for accuracy. That is the first step.

Then, make sure the device comes with a cuff, or that you can separately purchase a cuff, that was made with that device that fits your arm. Know your arm circumference so you can find the correct size cuff. Do not use an off-brand cuff. The device’s accuracy is tied to the cuff.

What else are you and your colleagues working on with respect to BP measurement?

Brady: It is so important to make sure people who measure BP follow all the recommended steps. You can have the most accurate measurement device and the appropriately sized cuff, but if you do not take all of those steps, you may not be guaranteed an accurate BP measurement.

We are trying to figure out ways to simplify the BP measurement process. We have been identifying BP steps deemed to be essential for accuracy and trying to determine what is really essential. We already conducted a study looking at the impact of resting prior to BP measurement. We found that if you do not have high BP you can probably take a person’s BP immediately upon sitting. However, if the person’s BP is high, you should re-take it after they have rested for 5 minutes.

The BP cuff should be placed at mid-heart level. We are now looking at the impact of measuring BP if the person’s arm is not resting in that way, perhaps resting to the side of the body. We are also assessing the impact of ambient noise in the room during a BP measurement.