Blood pressure monitors are all the same, right? Wrong

ACCURATE measurement of blood pressure is one of the most common and important medical tests that can be performed. Most people are familiar with how this is undertaken, using a blood pressure measurement device and a cuff inflated over the upper arm.

If an individual is diagnosed with hypertension, it is possible to intervene with medication or lifestyle changes to lower blood pressure and thereby reduce the risk for future cardiovascular disease events, especially stroke, acute myocardial infarction and kidney disease.

Correct diagnosis of high blood pressure requires careful measurement as there are many sources of potential error, some of which are well known – such as the “white coat effect” that can produce an acute elevation in blood pressure. With traditional auscultatory monitoring using mercury or aneroid sphygmomanometers not being recommended anymore due to challenges of noise interference, calibration issues, mercury toxicity and preference of observers to select round numbers, the World Health Organization now recommends automated upper arm devices to be used for monitoring.

But one source of error associated with automated devices that is generally unknown and comes as a surprise, particularly for health professionals, is that most automated blood pressure devices have never undergone accuracy testing to ensure the validity of readings according to recommended scientific standards.

A common misconception is that regulatory approval by the Therapeutic Goods Administration (or the US Food and Drug Administration) reflects device accuracy, but this is not the case.

Accuracy testing should be carried out by trained personnel and involves careful comparison with reference blood pressure measurements among a group of at least 85 people, comprising both men and women, across a range of blood pressures and different arm sizes.

Our recent JAMA publication showed that only 23% of upper arm cuff devices sold globally were validated according to recommended standards, and unfortunately this is similarly replicated in Australia where, in 2020, only 18% of devices available for online purchase had proof of validation.

Blood pressure devices that have not undergone recommended accuracy testing are more likely to produce more variable and inaccurate readings, thus adversely influencing correct diagnosis and medical care.

The extent to which medical care is compromised is not fully known, but even relatively small errors at a population level (eg, 5 mmHg) have enormous consequences regarding hypertension prevalence and consequent allocation of health service resources.

The possible impact on individuals is not hard to imagine. Unnecessary medications may result from erroneously overestimated blood pressure, whereas an opportunity to reduce risk of stroke and other clinical events through appropriate prescription of medication may be missed where blood pressure is erroneously underestimated.

Either outcome from inaccurate blood pressure measurement creates additional costs to the community and health systems that could otherwise be avoided.

How could a problem like this have been created around such an important medical device as one that measures blood pressure?

A key contributory factor is a regulatory loophole that enables manufacturers to perform in-house accuracy testing, without necessarily following recommended testing standards and without obligation to publicly reveal the results of those tests.

In different world regions, weak or absent regulations allow the regulatory clearance for marketing and sale of blood pressure devices without rigorous accuracy testing.

Worldwide, 360 companies manufacture over 2400 different models of upper arm cuff blood pressure devices. These medical devices can be sold via the internet and delivered across international borders, circumventing regulatory surveillance in some cases.

GPs may be using non-validated blood pressure devices unknowingly, and pharmacists may stock a range of non-validated devices unknowingly. Patients may also be purchasing non-validated devices with intent to monitor their blood pressure at home, but without awareness of validation status.

For those at risk, home blood pressure monitoring is recommended in Australia and by most hypertension societies worldwide because well designed studies using appropriately validated devices show that home blood pressure provides superior diagnosis (and greater association with clinical events) compared with clinic measured blood pressure.

Further compounding the issue in Australia is that non-validated blood pressure devices are cheaper than those that have been validated (by about 25%), thus potentially drawing consumers unwittingly towards preferential purchase of less accurate devices.

What can be done to rectify these problems?

There is no simple solution, as effort is required across a range of stakeholders including government regulatory organisations, non-government organisations, manufacturers, researchers, health professionals, and consumers.

A key action is to legislate for mandatory validation of blood pressure devices according to one recommended international standard before devices can be approved for sale.

Widespread education is also needed.

This article published in The Conversation on home blood pressure measurement was written for health practitioners and the general community. It contains links to resources on how to check the validation status of a blood pressure device, how to correctly measure and record home blood pressure (paper or electronic diary). As well as tips on behaviour changes to help reduce blood pressure.

With elevated blood pressure occurring in one in three adults in Australia, it is not surprising that it is the most frequently managed problem in general practice. More automated blood pressure devices are now being used in general practice, pharmacies and at home, but we need a lightbulb moment in Australia.

Not all blood pressure devices are created equal. All end-users should become aware of the potential accuracy problems of devices that have not been validated for accuracy, and call for regulations to enforce that all devices sold should meet international validation standards.

Author bios to come …

James Sharman is a Professor of Medical Research and Deputy Director at the Menzies Institute for Medical Research, Hobart. He chairs a project of the Lancet Commission on Hypertension Group with the goal of increasing the global availability of blood pressure devices that have been validated for accuracy.

Dean Picone is a Postdoctoral Research Fellow at the Menzies Institute for Medical Research, Hobart. He works on various projects related to the accurate measurement of blood pressure.

Aletta Schutte is a Professor of Cardiovascular Medicine and Principal Theme Lead of Cardiac Vascular and Metabolic Medicine at UNSW Sydney and the George Institute for Global Health. She is the immediate Past President of the International Society of Hypertension.

The statements or opinions expressed in this article reflect the views of the authors and do not represent the official policy of the AMA, the MJA or InSight+ unless so stated.