Is ambulatory blood pressure monitoring a useful tool for diagnosing hypertension?

Objective: To explore the usefulness of ambulatory blood pressure monitoring when diagnosing hypertension.Design: Comparison between office and ambulatory blood pressure.Setting: Primary Health Care Centre in southern Sweden.Subjects: Previously untreated hypertensives found in a blood pressure screening project concerning middleaged men and women and normotensive controls chosen from the same population.Methods: Comparison between repeated office blood pressures and a single-day ambulatory blood pressure recording in untreated hypertensives and normotensives. Data were compared individually for each patient.Results: The percentage of hypertensives and normotensives ‘correctly’ diagnosed by office-BP depends on where the dividing line between normal and increased ambulatory blood pressure is drawn. No established cut-off point exists, but 85–90 mmHg for diastolic blood pressure has been proposed.When 85 mmHg was used, 94% of the hypertensives and 84% of the normotensives were correctly diagnosed. When instead 90 mmHg was used, the figures were 72% and 97%, respectively.Conclusions: Although hypertensives and normotensives were well separated by office blood pressure, an overlap in day mean ambulatory blood pressure was found between the hypertensives and the normotensives. This overlap varied considerably within the small range of 5 mmHg for diastolic day mean blood pressure. How to interpret and use this information is not obvious, since we do not know if a single day or 24 hour ambulatory blood pressure recording better predicts the risks of cardiovascular disease than do repeated office blood pressure measurements. It therefore seems reasonable that office blood pressure remains the standard for diagnosing hypertension in clinical practice until we have enough data on ambulatory monitoring from prospective studies.