The British Medical Journal has published the results of a prospective cohort study that aimed to derive age and sex related ambulatory blood pressure equivalents to clinic blood pressure thresholds for diagnosis and treatment of hypertension.
The study was conducted in 11 centres in Australia and involved 8,529 participants. Ambulatory results were compared to those taken by trained staff and also doctors.
The mean blood pressure measured by trained staff while the patient was seated as 142/82mmHg compared to 150/89mmHg when measured by a doctor. The measurements taken by trained staff were 6/3mmHg higher than daytime ambulatory blood pressure and 10/5mmHg higher than 24 hour blood pressure. The authors also note that the closer the patient’s blood pressure is to normal levels, the closer is the agreement between daytime ambulatory and clinic blood pressure.
This study adds weight the information contained in the NICE guideline for Hypertension which indicates that ambulatory readings are commonly lower than clinic readings by between 10/5mmHg and 20/10mmHg.
The authors conclude that, "these results provide a framework for the diagnosis and management of hypertension using ambulatory blood pressure values".
Action: Clinicians who use and interpret ambulatory blood pressure measurements may find the figures reported in this study useful for identifying thresholds for initiation or changes to treatment.