Self-measurement of blood pressure at home: is it reliable?

Accuracy of blood-pressure monitors owned by patients with hypertension (ACCU-RATE study): a cross-sectional, observational study in central England

Background

Home blood-pressure (BP) monitoring is recommended in guidelines and is increasingly popular with patients and health professionals, but the accuracy of patients’ own monitors in real-world use is not known.

Aim

To assess the accuracy of home BP monitors used by people with hypertension, and to investigate factors affecting accuracy.

Design and setting

Cross-sectional, observational study in urban and suburban settings in central England.

Method

Patients (n = 6891) on the hypertension register at seven practices in the West Midlands, England, were surveyed to ascertain whether they owned a BP monitor and wanted it tested. Monitor accuracy was compared with a calibrated reference device at 50 mmHg intervals between 0–280/300 mmHg (static pressure test); a difference from the reference monitor of +/−3 mmHg at any interval was considered a failure. Cuff performance was also assessed. Results were analysed by frequency of use, length of time in service, make and model, monitor validation status, purchase price, and any previous testing.

Results

In total, 251 (76%, 95% confidence interval [95% CI] = 71 to 80%) of 331 tested devices passed all tests (monitors and cuffs), and 86% (CI] = 82 to 90%) passed the static pressure test; deficiencies were, primarily, because of monitors overestimating BP. A total of 40% of testable monitors were not validated. The pass rate on the static pressure test was greater in validated monitors (96%, 95% CI = 94 to 98%) versus unvalidated monitors (64%, 95% CI = 58 to 69%), those retailing for >£10 (90%, 95% CI = 86 to 94%), those retailing for ≤£10 (66%, 95% CI = 51 to 80%), those in use for ≤4 years (95%, 95% CI = 91 to 98%), and those in use for >4 years (74%, 95% CI = 67 to 82%). All in all, 12% of cuffs failed.

Conclusion

Patients’ own BP monitor failure rate was similar to that demonstrated in studies performed in professional settings, although cuff failure was more frequent. Clinicians can be confident of the accuracy of patients’ own BP monitors if the devices are validated and ≤4 years old.

[Lancet Commission on Hypertension Group position statement on the global improvement of accuracy standards for devices that measure blood pressurePosicionamento do Grupo da Lancet Commission on Hypertension sobre a melhoria global dos padrões de acurácia para aparelhos que medem a pressão arterial]

The Lancet Commission on Hypertension identified that a key action to address the worldwide burden of high blood pressure (BP) was to improve the quality of BP measurements by using BP devices that have been validated for accuracy. Currently, there are over 3 000 commercially available BP devices, but many do not have published data on accuracy testing according to established scientific standards. This problem is enabled through weak or absent regulations that allow clearance of devices for commercial use without formal validation. In addition, new BP technologies have emerged (e.g. cuffless sensors) for which there is no scientific consensus regarding BP measurement accuracy standards. Altogether, these issues contribute to the widespread availability of clinic and home BP devices with limited or uncertain accuracy, leading to inappropriate hypertension diagnosis, management and drug treatment on a global scale. The most significant problems relating to the accuracy of BP devices can be resolved by the regulatory requirement for mandatory independent validation of BP devices according to the universally-accepted International Organization for Standardization Standard. This is a primary recommendation for which there is an urgent international need. Other key recommendations are development of validation standards specifically for new BP technologies and online lists of accurate devices that are accessible to consumers and health professionals. Recommendations are aligned with WHO policies on medical devices and universal healthcare. Adherence to recommendations would increase the global availability of accurate BP devices and result in better diagnosis and treatment of hypertension, thus decreasing the worldwide burden from high BP.

Lancet Commission on Hypertension group position statement on the global improvement of accuracy standards for devices that measure blood pressure

: The Lancet Commission on Hypertension identified that a key action to address the worldwide burden of high blood pressure (BP) was to improve the quality of BP measurements by using BP devices that have been validated for accuracy. Currently, there are over 3000 commercially available BP devices, but many do not have published data on accuracy testing according to established scientific standards. This problem is enabled through weak or absent regulations that allow clearance of devices for commercial use without formal validation. In addition, new BP technologies have emerged (e.g. cuffless sensors) for which there is no scientific consensus regarding BP measurement accuracy standards. Altogether, these issues contribute to the widespread availability of clinic and home BP devices with limited or uncertain accuracy, leading to inappropriate hypertension diagnosis, management and drug treatment on a global scale. The most significant problems relating to the accuracy of BP devices can be resolved by the regulatory requirement for mandatory independent validation of BP devices according to the universally-accepted International Organisation for Standardization Standard. This is a primary recommendation for which there is an urgent international need. Other key recommendations are development of validation standards specifically for new BP technologies and online lists of accurate devices that are accessible to consumers and health professionals. Recommendations are aligned with WHO policies on medical devices and universal healthcare. Adherence to recommendations would increase the global availability of accurate BP devices and result in better diagnosis and treatment of hypertension, thus decreasing the worldwide burden from high BP.

How Accurate Are Home Blood Pressure Devices in Use? A Cross-Sectional Study

Background

Out of office blood pressure measurements, using either home monitors or 24 hour ambulatory monitoring, is widely recommended for management of hypertension. Though validation protocols, meant to be used by manufacturers, exist for blood pressure monitors, there is scant data in the literature about the accuracy of home blood pressure monitors in actual clinical practice. We performed a chart review in the blood pressure assessment clinic at a tertiary care centre.

Methods

We assessed the accuracy of home blood pressure monitors used by patients seen in the nephrology clinic in Ottawa between the years 2011 to 2014. We recorded patient demographics and clinical data, including the blood pressure measurements, arm circumference and the manufacturer of the home blood pressure monitor. The average of BP measurements performed with the home blood pressure monitor, were compared to those with the mercury sphygmomanometer. We defined accuracy based on a difference of 5 mm Hg in the blood pressure values between the home monitor and mercury sphygmomanometer readings. The two methods were compared using a Bland-Altman plot and a student’s t-test.

Results

The study included 210 patients. The mean age of the study population was 67 years and 61% was men. The average mid-arm circumference was 32.2 cms. 30% and 32% of the home BP monitors reported a mean systolic and diastolic BP values, respectively, different from the mercury measurements by 5 mm Hg or more. There was no significant difference between the monitors that were accurate versus those that were not when grouped according to the patient characteristics, cuff size or the brand of the home monitor.

Conclusions

An important proportion of home blood pressure monitors used by patients seen in our nephrology clinic were inaccurate. A re-validation of the accuracy and safety of the devices already in use is prudent before relying on these measurements for clinical decisions.

Regular use of a home blood pressure monitor by hypertensive adults--HealthStyles, 2005 and 2008

The authors analyzed HealthStyles surveys 2005 and 2008 combined to assess the prevalence of regular home blood pressure monitor (HBPM) use among hypertensive adults. All data were self-reported. The authors calculated odds ratios (ORs) of regular HBPM use and relative percent change (RPC) in the use of HBPM between the 2 survey years. There were 3739 (32.6%) hypertensives in the 2 survey years combined. Based on the self-reported data, the proportion of hypertensives who regularly used an HBPM was 43.2%. Male sex, age, race/ethnicity, household income, and education were all associated with differences in the prevalence of regular HBPM use. Patients 65 years and older (OR, 2.38; 95% confidence interval [CI], 1.49-3.81) were significantly more likely to be regular HBPM users than those 18 to 34 years. Non-Hispanic blacks were significantly less likely (OR, 0.69; 95% CI, 0.55-0.86) to be regular HBPM users than non-Hispanic whites. From 2005 to 2008, the RPC in regular HBPM use was 14.2% (from 40.1% to 45.8%); the largest RPCs were for the 3 youngest age groups, men, non-Hispanic blacks, and those with a household income of $40,000 to 59,900. Because HBPM has been demonstrated to aid in hypertension control, health care professionals should promote its use especially among hypertensives who are younger, non-Hispanic blacks, Hispanics, or with a lower income.

The influence of self-owned home blood pressure monitoring (HBPM) on primary care patients with hypertension: a qualitative study

Background

Home blood pressure monitoring (HBPM) is gaining popularity among hypertensive patients. This study aimed to explore the influence of self-initiated HBPM on primary care patients with hypertension.

Methods

Six in-depth interviews and two focus group discussions were conducted, taking into consideration the experiences of 24 primary care patients with hypertension. These patients had been using HBPM as part of their hypertension management. The overriding influences were grouped under themes which emerged from analyzing the data using the grounded theory approach.

Results

There are both positive and negative influences of self-initiated HBPM. Patients used the readings of their HBPM to decide on many aspects of their hypertension management. The HBPM readings both influenced their adherence to diet and exercise and provided certain reassurance when they experienced symptoms. In addition, the act of discussing their HBPM readings with their health care providers resulted in an enhanced doctor-patient therapeutic relationship. Nevertheless, HBPM created confusion at times in some patients, particularly with regard to the target blood pressure level and the need for medication. This led to some patients making their own medical decisions based on their own standards.

Conclusions

HBPM is becoming an integral part of hypertension management. Primary care patients who self-initiated HBPM reported being more self-efficacious, but lack of participation and guidance from their doctors created confusion, and hindered the true benefit of HBPM.

Proposal of a method for the evaluation of inaccuracy of home sphygmomanometers

OBJECTIVE

There is no formal protocol for evaluating the individual accuracy of home sphygmomanometers. The aims of this study were to propose a method for achieving accuracy in automated home sphygmomanometers and to test the applicability of the defined method. The purposes of this method were to avoid major inaccuracies and to estimate the optimal circumstance for individual accuracy.

METHODS

The method has three stages and sequential measurement of blood pressure is used. The tested devices were categorized into four groups: accurate, acceptable, inaccurate and very inaccurate (major inaccuracy). The defined method takes approximately 10 min (excluding relaxation time) and was tested on three different occasions.

RESULTS

The application of the method has shown that inaccuracy is a common problem among non-tested devices, that validated devices are superior to those that are non-validated or whose validation status is unknown, that major inaccuracy is common, especially in non-tested devices and that validation does not guarantee individual accuracy.

CONCLUSION

A protocol addressing the accuracy of a particular sphygmomanometer in an individual patient is required, and a practical method has been suggested to achieve this. This method can be modified, but the main idea and approach should be preserved unless a better method is proposed. The purchase of validated devices and evaluation of accuracy for the purchased device in an individual patient will improve the monitoring of self-measurement of blood pressure at home. This study addresses device inaccuracy, but errors related to the patient, observer or blood pressure measurement technique should not be underestimated, and strict adherence to the manufacturer's instructions is essential.

Home sphygmomanometers: validation versus accuracy

OBJECTIVE

The validation and accuracy of sphygmomanometers are important issues in the home sphygmomanometer market and in clinical practice. The aims of this study are to assess the frequency of validated home sphygmomanometers and to evaluate the relationship between the validation and accuracy of the devices.

METHODS

Eight hundred and ninety-six home sphygmomanometers were brought by individuals to the University Hospital Hypertension Clinic for this study, and 870 (97%) of the devices were in adequate working condition and suitable for analysis. The relationship between accuracy and validation was investigated only in automated sphygmomanometers (n = 554).

RESULTS

Both the manufacturer and model were known in 500 devices (90%), and these devices were eligible for evaluation of validation. We found 74 devices listed in the dabl Educational Trust website. Twenty-two of the 74 (30%) devices were validated. Four hundred (72%) of the 554 automated sphygmomanometers were inaccurate. The frequency of accuracy was higher among validated devices compared with nonvalidated devices (68 vs. 15%) (P<0.01).

CONCLUSION

Our study showed that the frequency of accurate devices was higher among validated sphygmomanometers compared with nonvalidated sphygmomanometers. To our knowledge, our study is the first to demonstrate the relationship between accuracy and validation of home sphygmomanometers. The frequency of device-related errors can be decreased by training patients and supervising the blood pressure device market. Nonprofit organizations can help patients to overcome some of the problems in the blood pressure device market.