A newly developed method that improves the accuracy of ankle blood pressure measurements could transform care for people who are unable to have their blood pressure taken from the arm.
Researchers from the University of Exeter Medical School, in a 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 to create a personalized predictive model. This model enables healthcare professionals to estimate arm blood pressure more precisely using ankle readings (when compared with earlier approaches). To make the process easier to use, the team has also launched an online calculator that helps both clinicians and patients interpret ankle-based results.
Why Accuracy in Blood Pressure Measurement Matters
More than one billion people worldwide live with high blood pressure, a major risk factor for heart disease, stroke, and kidney problems. Reliable measurements are crucial for diagnosing and managing the condition effectively.
Although blood pressure is typically measured on the upper arm, some people cannot have it taken there due to disability, limb loss, or conditions such as stroke. In such cases, readings are taken from the ankle. However, ankle measurements are usually higher than arm readings, and because treatment guidelines are based on arm data, this difference can lead to inaccurate diagnoses and inappropriate treatment decisions.
Improving Accuracy and Reducing Misdiagnoses
Professor Chris Clark, who led the research, explained: "Our new method will give a more accurate blood pressure reading for around two percent more people. This doesn't sound 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."
To achieve this, the researchers used statistical modeling on data from 33,710 people (mean age 58 years, 45 per cent female) across multiple countries. The analysis explored the relationship between arm and ankle blood pressures, developed a predictive equation for estimating arm values from ankle readings, and examined how ankle readings relate to important health outcomes (such as heart attack risk).
This advancement could help close a significant health gap by providing accurate and personalized blood pressure results for people who have been excluded from standard monitoring. It is estimated that up to 10,000 adults in the UK live with upper limb loss, while 75 per cent of the country's 1.3 million stroke survivors experience upper limb difficulties that can make arm-based measurements challenging or impossible.
The project received support from the Stroke Association and the Thalidomide Trust, two organizations advocating for people affected by these conditions.
Expert Reactions and Public Health Impact
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 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 paper titled "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" is published in BMJ Open.
The online calculator is available at: ABLE-BP Tool -- https://ablebp.research.exeter.ac.uk/[1]
"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."