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 increasingly popular with patients and health care 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 investigate factors affecting accuracy. Design and Setting Patients on the hypertension register at seven practices in central England were surveyed to ascertain if they owned a monitor and wanted it tested. Method Monitor accuracy was compared to a calibrated reference device, at 50 mmHg intervals between 0-280/300 mmHg (static pressure test), with a difference from the reference monitor of +/-3 mmHg at any interval considered a failure. Cuff performance was also assessed. Results were analysed by usage rates, length of time in service, make and model, monitor validation status, cost, and any previous testing. Results 251 (76%, 95% CI 71-80%) of 331 tested devices passed all tests (monitors and cuffs) and 86% passed the static pressure test, deficiencies primarily due to overestimation. 40% of testable monitors were unvalidated. Pass rate on the static pressure test was greater in validated monitors (96% [95% CI 94-98%] vs 64% [95% CI 58-69%]), those retailing for over £10, and those in use for less than four years.12% of cuffs failed. Conclusion Patients’ own BP monitor failure rate was similar to that in studies performed in professional settings, though cuff failure was more frequent. Clinicians can be confident of the accuracy of patients’ own BP monitors, if validated and less than five years old.