Background: Ambulatory blood pressure monitoring was introduced more than 40 years ago and is accepted as a clinically useful method to evaluate the white coat effect in patients with suspected and established hypertension.
Aim: To study the differences between blood pressure readings taken in the physician's office in the primary healthcare setting, and ambulatory readings, and to find possible predictors.
Design of study: Prospective study.
Setting: Two primary healthcare centres in Norway.
Method: The study included 221 patients, 107 of whom were on antihypertensive treatment, and 114 of whom were under investigation for possible hypertension. Differences between blood pressure readings taken in the physician's office and ambulatory readings were calculated. Independent predictors for the white coat effect were calculated using linear regression analysis.
Results: The difference between blood pressure readings taken in the office and ambulatory readings was 27 mmHg systolic and 11 mmHg diastolic. For the systolic readings, the following factors were independent predictors of the amount of the white coat effect: mean blood pressure, age, history of smoking, family history of cardiovascular disease, and antihypertensive treatment. For the diastolic readings, they were: mean blood pressure, history of smoking, and sex of the patient (with this being most significant for women).
Conclusion: Ambulatory blood pressure measurement is of significant value in identifying patients with white coat hypertension. It can be an important supplement for use in the diagnosis and follow-up of patients with hypertension in general practice.