In a recent study, scientists found the most common method of measuring blood pressure is often inaccurate.
The finding suggests people at risk of heart disease are missing diagnosis and potentially life-saving treatment.
The commonly used so-called “cuff method” involves strapping an inflatable cuff over the upper arm to temporarily cut off the blood supply; then calculating the blood pressure once the cuff is relaxed.
In the study, the team found this method can be inaccurate when monitoring people with mid-range blood pressure.
They used data from studies from the 1950s until now that compared cuff blood pressure of more than 2,500 people with that of the gold standard method, called invasive blood pressure.
It’s uncertain whether cuff blood pressure accurately measures the pressure in the arteries of the arm or the major artery just outside the heart, called the aorta.
This is important as blood pressure readings can be different in these two spots – a potential difference of 25 mmHg or more.
The central aorta blood pressure is a better indicator of the pressure experienced by organs, such as the heart and brain, so it is more clinically relevant.
The possibility of big blood pressure differences between the arm and the aorta could result in very different clinical decisions on diagnosis and treatment.
The team found cuff blood pressure had reasonable accuracy compared with the reference standard, at either the arm or aorta, among people with low cuff blood pressure (lower than 120/80 mmHg) and high cuff blood pressure (the same or higher than 160/100 mmHg).
These people are at the extreme ends of the blood pressure risk spectrum.
The team showed the accuracy when compared to invasive blood pressure was up to 80%.
But for the rest of the population with blood pressure in the middle range – systolic 120 to 159, and diastolic 80 to 99 mmHg – accuracy compared with invasive blood pressure at the arm or the aorta was quite low: only 50% to 57%.
The findings suggest that for people whose blood pressure is in the most common mid-range of 120 to 160 mmHg systolic or 80 to 100 mmHg diastolic, there can be much less certainty as to whether the cuff blood pressure is truly representative of the actual blood pressure.
While this study reveals accuracy issues, the evidence from many large clinical trials clearly shows taking medication to lower blood pressure from high levels reduces the chances of stroke, heart attack and vascular disease.
The team says cuff blood pressure measurements are still useful, but doctors could help more people if we could measure blood pressure more accurately.
If you care about high blood pressure, please read studies about how fasting may help reverse high blood pressure, and early time-restricted eating could help improve blood pressure.
For more information about blood pressure, please see recent studies about new suggestions for treating high blood pressure, and results showing vitamin D could improve blood pressure in people with diabetes.
The study was published in the Journal of the American College of Cardiology.
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