Researchers at the University of Exeter have developed a predictive model and online calculator to estimate arm blood pressure from ankle readings, aiding those unable to use standard arm tests. The innovation, based on data from over 33,000 people, could reduce misdiagnoses for thousands globally. Published in BMJ Open, the method addresses a key gap in hypertension management.
High blood pressure affects more than one billion people worldwide and is a leading risk factor for heart disease, stroke, and kidney problems. While arm measurements are standard, they are not possible for everyone due to disabilities, limb loss, or conditions like stroke. In such cases, ankle readings are used, but these are typically higher than arm values, potentially leading to inaccurate diagnoses since treatment guidelines rely on arm data.
A team from the University of Exeter Medical School, led by Professor Chris Clark, analyzed data from 33,710 individuals (mean age 58 years, 45 percent female) across multiple countries. Funded by the National Institute for Health and Care Research (NIHR) and supported by the Stroke Association and Thalidomide Trust, the study created a personalized predictive equation to convert ankle systolic blood pressure to arm equivalents. This approach improves accuracy compared to prior methods and links ankle readings to health outcomes like heart attack risk.
Professor Clark 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."
The tool is particularly relevant in the UK, where up to 10,000 adults live with upper limb loss and 75 percent of the 1.3 million stroke survivors face upper limb difficulties. Juliet Bouverie OBE, CEO of the Stroke Association, noted: "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."
Professor Kevin Munro, Director of NIHR's Research for Patient Benefit Programme, added: "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 study, 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," appears in BMJ Open (2025; 15(6): e094389). An online calculator is available at https://ablebp.research.exeter.ac.uk/.
Sue Kent, a 62-year-old TV presenter from Swansea with Thalidomide-induced upper limb disability, shared her experience: "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."