White coat effect 'surprisingly high'
GPs have been urged to confirm hypertension with ambulatory blood pressure tests before starting drug therapy after a study suggested the 'white coat effect' on raising blood pressure was surprisingly great- er than previously thought.
Average systolic blood pressure was 27mmHg higher when patients were tested in primary care compared with when ambulatory testing was used, the study in this month's British Journal of General Practice suggested.
The prospective study examined blood pressure readings in 221 Norwegian patients, 107 on antihypertensive drugs and 114 under investigation for suspected hypertension.
White coat hypertension was defined as a mean daytime reading of less than 135mmHg systolic and less than 85mmHg diastolic.
Three-quarters of patients showed a difference of at least 15mmHg in systolic blood pressure when readings in the two settings were compared. Some 52 per cent had a diastolic blood pressure difference of 10mmHg or more.
Age, history of smoking, family history of cardiovascular disease, mean blood pressure and antihypertensive treatment and female gender predicted significant white coat effect in patients tested in primary care.
GPs could use the predictors to pinpoint patients with a greater chance of white coat hypertension, the researchers from the department of
general practice and primary care at the University of Oslo said.