Serial measurements to diagnose hypertension
Ambulatory blood pressure monitoring is recommended when an accurate assessment of blood pressure is needed. As this is costly and time-consuming, Dutch researchers have been looking for a more convenient approach.
They studied 84 patients who had been referred for 24-hour ambulatory blood pressure monitoring. About half the patients were already taking antihypertensive drugs.
Before the patients began their monitoring, they had their blood pressures checked in a quiet room. It was measured every five minutes for 30 minutes, using the same automatic device that was to be used for 24-hour monitoring.
The systolic blood pressure measured in the clinic fell for the first three readings. They then settled to a plateau. Diastolic blood pressures followed a similar pattern. The mean blood pressure was the same at 15, 20, 25 and 30 minutes.
When the mean blood pressures were compared with those of ambulatory blood pressure monitoring, there was little difference. Using the 30-minute measurements correctly classified 87% of patients into the correct subtype of hypertension.
Hypertension cannot be diagnosed with a single measurement of blood pressure. Many people are anxious when they consult, which may lead to white-coat hypertension.
The 30-minute measurements identified as many cases of white-coat hypertension as ambulatory monitoring did. They also found a similar number were normotensive.
While a brief series of measurements may help diagnose hypertension, it is not a substitute for 24-hour monitoring.
Dr John Dowden, Canberra
Van der Wel MC, et al A novel approach to office blood pressure measurement. Annals of Family Medicine 2011;9:128-135
Tags: , Research Update