Researchers find uncertainty in accuracy of blood pressure measurements

A comprehensive analysis of blood pressure data from the 1950s to the present day has highlighted the need for improvement in the accuracy of blood pressure measuring.

Researchers at the University of Tasmania’s Menzies Institute for Medical Research found significant uncertainty in the accuracy of blood pressure measured with an upper arm cuff in those people with mid-range blood pressure (the most common range). The study is published today (Tuesday, 25^th July 2017) in the Journal of the American College of Cardiology.

To undertake the study researchers analyzed almost seven decades of international data on 2,500 people who had had their blood pressure measured simultaneously with an upper arm cuff and with a catheter inside the artery either at the arm or at the aorta (the gold standard reference method).

They found much lower certainty that cuff measurements were accurate in those people whose blood pressure was in the mid-range (120 to 160 mmHg systolic blood pressure or 80 to 100 mmHg diastolic blood pressure) than those whose cuff-measured blood pressure was either low (below 120/80 mmHg) or high (over 160/100 mmHg). The researchers found reasonable confidence that the values for high and low blood pressure were a good representation of the actual blood pressure.

The central aorta blood pressure is more clinically relevant because this is a better indicator of the pressure experienced by the organs (for example the heart and brain), in contrast to the pressure in the arm. However, the data showed that large differences in blood pressure can occur between the artery at the arm and the central aorta.

Professor James Sharman said the possibility of big differences in blood pressure measurements between the arm and the aorta had implications for clinical decisions around diagnosis and treatment.

“These findings tell us that we need to improve the accuracy of blood pressure measuring devices,” Professor Sharman said.

He stressed that the findings did not mean that people should stop taking their medication or stop having their blood pressure measured with the cuff device.

“While this study reveals accuracy issues, the evidence from many large clinical trials clearly shows that taking medication to lower blood pressure from high levels reduces the chances for stroke, heart attack and vascular disease. So we are doing reasonably well with current methods, but we would be able to help more people if we could measure blood pressure more accurately.”

Until the accuracy standards of blood pressure measuring devices are improved, the best available methods to confirm blood pressure levels are by taking the average of many repeated measures. People can have repeated measures taken in consultation with their general practitioners or at specialist centers. The ways of measuring over time include self-measured home blood pressure, 24-hour ambulatory blood pressure, and automated unobserved blood pressure.