Collaboration for Academic Primary Care (APEx) Blog
Collaboration for Academic Primary Care (APEx) Blog
Posted by ma403
20 October 2023Chris Clark
Clinical Senior Lecturer
19th October 2023
We usually measure blood pressure by compressing the upper arm then gradually releasing that compression, taking note of the pressure at which blood can flow again. This method is largely unchanged since first demonstrated in 1896. Devices have evolved, methods for detecting blood flow have changed, and portable devices have allowed measurements at home or when active, but the principles remain the same.
One might assume, therefore, that we know enough about how to measure blood pressure. Various international guidelines tell us precisely how to do this; they are regularly updated to take account of new evidence. However, not all guidance is based on evidence; it is estimated that up to half of all primary care recommendations are, in fact, based on expert opinion alone.
This can include quite fundamental elements of guidelines. It was recognised that blood pressure may not be the same in both arms in the 1900s, and since the 1930s all international guidelines have advised that the higher reading from the left or right arms should be used for diagnosis and treatment of high blood pressure. This remained an expert consensus recommendation until this year. A lack of evidence might not matter if guidance is being followed, however, we previously found that up to 25% of general practitioners, when asked, did not routinely adopt the higher arm reading for routine care.
We set out to research which arm should be used for blood pressure measurement, using blood pressure measurements from both arms and survival data pooled from over 50,000 people in our INTERPRESS-IPD Collaboration. We conducted individual participant data meta-analyses, finding that using the higher arm blood pressure, compared to the lower arm, reclassified 12% of participants from below to above recognised hypertension thresholds. Further analyses showed that the higher rather than lower arm blood pressure more accurately predicted mortality and cardiovascular events over ten years, with improved classification of participants’ cardiovascular risks, thus ensuring that people can be offered the most appropriate choices for treatment high blood pressure and cardiovascular risk.
Our paper was published in Hypertension in 2022. Already downloaded over 10,000 times, it was cited in this year’s 2023 update to the European Society for Hypertension guidelines, filling that gap in the evidence as we hoped. The paper has now been highly commended in the Royal College of General Practitioners 2022 Research Paper of the Year awards – announced 19th October 2023. This is a welcome acknowledgment of the efforts made by a large research team and will spur us on to the next paper.
Read more about our INTERPRESS-IPD Collaboration at: Interpress-IPD | Health and Community Sciences | University of Exeter