A new method that improves the accuracy of interpreting blood pressure measurements taken at the ankle could be vital for individuals who are unable to have their blood pressure measured on the arm.

A newly developed approach could significantly improve how blood pressure readings taken at the ankle are interpreted, offering a vital solution for people who are unable to have their blood pressure measured on the arm.

Researchers at the University of Exeter Medical School have created a personalized predictive model designed to estimate arm blood pressure more accurately using ankle readings. The study, published in BMJ Open and funded by the National Institute for Health and Care Research (NIHR), analyzed data from more than 33,000 individuals worldwide. The team has also launched an online calculator to help both healthcare professionals and patients make sense of ankle readings with greater precision.

High blood pressure affects more than one billion people across the globe and is a leading contributor to heart disease, stroke, and kidney problems. Because of these risks, ensuring that blood pressure is measured and interpreted correctly is crucial. In most cases, the arm is used for these measurements, but for some people—such as those with disabilities, missing limbs, or movement difficulties after a stroke—this isn't possible.

In such situations, measurements can be taken at the ankle. However, ankle readings tend to be higher than those from the arm, and since current treatment guidelines are based solely on arm measurements, this difference can make accurate diagnosis difficult and increase the likelihood of errors.

The New Predictive Model and Its Impact

Professor Chris Clark from the University of Exeter Medical School led the study and said: "Our new method will give a more accurate blood pressure reading for around two percent more people. This doesn't sound like a big number, but remember, around a third of adults have high blood pressure and once you get into your 60s, it's more than half of the adults. The NHS Health Check Programme diagnoses 38,000 new cases annually in England alone, so two percent equates to 750 fewer potential misdiagnoses per year in England, and tens of thousands globally."

Researchers used statistical modeling on arm and ankle blood pressure readings from 33,710 people (mean age 58 years, 45 percent female) across the world to help describe the relationship between arm and ankle blood pressures, predict arm blood pressure using ankle blood pressure readings, and predict important health outcomes (such as risk of heart attacks) from ankle blood pressure readings.

Addressing Health Inequalities

This research could help address a health inequality by providing accurate and personalized blood pressure measurements for people who previously could not have their blood pressure measured accurately from their arm. It's estimated there are up to 10,000 adults currently living in the UK with upper limb loss, while 75 percent of the country's 1.3 million stroke survivors have upper limb dysfunction, sometimes making it difficult to measure blood pressure from their arm.

The study was supported by the Stroke Association and Thalidomide Trust.

Juliet Bouverie OBE, CEO of the Stroke Association, said: "Someone in the UK has a stroke every five minutes, with high blood pressure accounting for around half of those. Around two-thirds of stroke survivors will leave the hospital with some form of disability, including paralysis in an arm, which can prevent getting accurate blood pressure readings from the affected limb. Many stroke survivors feel anxious about having another stroke, so receiving an accurate blood pressure reading in the ankle will not only provide benefits in the primary prevention of stroke, but importantly in easing the minds of stroke survivors who are already dealing with the devastating impact of stroke."

Professor Kevin Munro, Director of NIHR's Research for Patient Benefit Programme, said: "This research has identified an ingenious solution to an important problem – finding a way to measure blood pressure for people who cannot have it monitored via the upper arm. Keeping track of blood pressure is a vital tool to help keep people healthy, and this NIHR-funded research will help to spot high blood pressure and treat it even more widely."

The online calculator is available at: ABLE-BP Tool

"Why should I not be able to have my blood pressure taken?"

TV presenter Sue Kent, 62, from Swansea, has an upper limb disability caused by the drug Thalidomide, which was prescribed to her mother during pregnancy. She has eight-inch arms, which aren't big enough for blood pressure to be taken.

Sue said: "I rarely had my blood pressure taken when I was younger, but when I did, I used to have a really big cuff they would put around my thigh and take the blood pressure there. Whether it was accurate or not, nobody worried, but I didn't seem to have blood pressure problems.

"But then I had a cataract operation, and somebody took my blood pressure from my ankle, and it was very high. They did it three times and every time it was high, and it made me very worried. They (medical staff) weren't worried and carried on and did the cataract operation, but I was quite distressed."

Sue was diagnosed with Meniere's disease in 2017, which is a rare inner ear condition which has left her partially deaf.

She said: "I was worried I was going to have a stroke because Meniere's can be an indicator the blood flow isn't going to the brain. I knew I couldn't have my blood pressure taken accurately, so I went privately to have dye injected to check everything was OK.

"As you get older, blood pressure is an important indicator of so many things, including things that could be seriously wrong. Prodding about in the dark and guessing isn't really a safe thing to do. You need the right information about your blood pressure."

Sue hopes this new method could potentially help her and thousands of others like her have something most of us take for granted – an accurate blood pressure reading.

She said: "Why should I not be able to have my blood pressure taken when it's available to most people and is a relatively simple thing to do?

"When you're disabled, you're more likely to die younger for a variety of reasons, so this resource tips the scales a bit more in our favor. This could put us on a level playing field with everybody else when it comes to blood pressure. It means reassurance and maybe an early diagnosis if something is wrong."

Reference: "Arm Based on LEg blood pressures (ABLE-BP): can systolic ankle blood pressure measurements predict systolic arm blood pressure? An individual participant data meta-analysis from the INTERPRESS-IPD Collaboration" by Sinead T J McDonagh, Fiona C Warren, James Peter Sheppard, Kate Boddy, Leon Farmer, Helen Shore, Phil Williams, Philip S Lewis, A Jayne Fordham, Una Martin, Victor Aboyans and Christopher Elles Clark, 1 June 2025, BMJ Open.
DOI: 10.1136/bmjopen-2024-094389

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