Level of blood pressure control in a hypertensive population when measurements are performed outside the clinical setting.

BACKGROUND

To determine whether the number of optimally controlled hypertensive patients is higher using self-measurement of blood pressure at home and ambulatory monitoring, compared to using conventional blood pressure measurements at the doctor's office.

METHOD

An observational, cross-sectional, multicentre, descriptive study of a random sample of 237 primary health care patients, known to be hypertensive, from Badajoz (Spain). Blood pressure was measured at the doctor's office and by self-measurement at home. Those patients showing good control by self-measurement were subjected to 24-hour ambulatory monitoring. Optimal control was understood as blood pressure < 140/90 mm Hg when measured at the doctor's office, and < 135/85 mm Hg when self-measured at home and by daytime ambulatory monitoring.

RESULTS

Mean systolic/diastolic measurements at the doctor's office and by self-measurement were 145.6/83.9 and 134.0/78.7 mm Hg, respectively (p < 0.000). In the population optimally controlled by self-measurement and who subsequently received ambulatory monitoring, the mean blood pressure was 121.8/73.4 and 125.6/76.2 mm Hg, respectively (p = 0.002; p < 0.000). When measured at the doctor's office blood pressure was controlled in about 29.5% (95% CI 23.7-35.3%) of patients, in 38% when self-measured (95% CI 31.4-44.2%; p < 0.000), and in 24.5% when it was confirmed through ambulatory monitoring (95% CI 15.4-33.6%). Sensitivity and positive predictive values of the office measurements for the detection of patients who were well-controlled by self-measurement were 50% and 64.3%, respectively, and 53.4% and 73.8% as regards ambulatory monitoring.

CONCLUSIONS

A higher level of control is achieved with self-measurement at home not confirmed by ambulatory monitoring. Therefore, the white coat effect does not seem to influence the percentage of well-controlled patients detected at the doctor's office. Office blood pressure does not appear to be useful in distinguishing which individual patients are optimally controlled.