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New Calculator Provides More Accurate Blood Pressure Estimation

OXFORD, UK – Although blood pressure can be an important tool in determining patient health, it, too, often is a moving target.

To try to remedy that, Oxford University researchers have developed a new way to estimate true underlying blood pressure, overcoming common problems in a clinical setting which can lead to misleading results. Their work, including an online calculator, was published recently in the journal Hypertension.

“One phenomenon where readings are higher in the clinic than at home is referred to as the ‘white coat effect.’ This can lead to people being started on blood pressure-lowering treatments they do not really need,” said study leader James Sheppard, PhD, in a statement. “A reverse effect is also seen — some patients have lower readings in the clinic than they would in normal life, meaning that they can miss out on treatment that they could potentially benefit from. Understanding and accounting for the scale of these home-clinic differences would improve diagnosis and treatment.”

For the study, researchers analyzed data from more than 2,000 patients, focusing on factors such as age, gender, body mass index, alcohol consumption, and tobacco use. They also reviewed blood pressure characteristics from multiple readings taken in clinics, including the difference between the first and last readings and the rate of change in blood pressure among others.

Overall, data from around 900 patients was used to build a model, identifying factors that affect the difference between home and clinic blood pressure readings. The model was then validated by checking the data against other patients in the study.

Resulting from those efforts is a prediction model that uses three separate blood pressure readings taken in a single consultation as well as basic patient characteristics. The model provides an adjusted blood pressure reading touted as significantly more accurate than existing models for identifying hypertension.

“We compared the accuracy of our model to the current UK NICE guidelines and those in use in the USA, Canada, and Europe,” Sheppard said. “It correctly classified 93% of cases, compared to the next best, the NICE guidelines, which correctly classified 78% of patients.”

While correctly classifying patients as hypertensive ensures they get the treatment they need, he added, “Perhaps just as importantly, this approach prevents those patients displaying a white coat effect from being put on treatment which they don't really need.”