A new method improving the accuracy of interpreting blood pressure measurements taken at the ankle could be crucial for people who cannot have their arm blood pressure measured.
New research from the University of Exeter Medical School, published in BMJ Open and funded by the National Institute for Health and Care Research (NIHR), analysed data from over 33,000 people to create a personalised predictive model for more accurately estimating arm blood pressure from ankle readings – when compared to previously available methods. The team has developed an online calculator for healthcare professionals and patients to interpret these readings effectively.
High blood pressure affects over one billion people globally, increasing the risk of serious health issues like heart, brain, and kidney diseases. It's therefore very important to measure and interpret blood pressure readings as accurately as possible. While blood pressure is typically measured on the arm, sometimes this is not possible due to disability, missing limbs, or problems caused by conditions such as stroke. Blood pressure can be measured at the ankle instead, but these readings are generally higher than arm values. Standard guidelines for treating blood pressure are based on arm readings only, which creates complications in making accurate estimations based on ankle measurements, potentially leading to misdiagnoses.
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 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 modelling on arm and ankle blood pressure readings from 33,710 people (mean age 58 years, 45 per cent 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.
This research could help address a health inequality by providing accurate and personalised 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 per cent 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 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.
