White-Coat Hypertension vs White-Coat Effect
ABPM (ambulatory blood pressure monitoring) is being used increasingly in clinical practices and it is indicated for:
a) the exclusion or confirmation of suspected white-coat hypertension;
b) the confirmation of a diagnosis of hypotension;
c) identifying patients with resistant hypertension
d) assessing drug efficacy
e) identifying masked hypertension.
In clinical practice, the most important indication for ambulatory blood pressure monitoring is to identify white-coat hypertension.
What is White-Coat Hypertension?
White-coat hypertension can be identified in untreated patients who have high blood pressure readings in the office but normal readings during usual daily activities outside clinical environment. White-coat hypertensive patients have elevated office blood pressure > 140 mmHg systolic and/or > 90 mmHg diastolic with a normal blood pressure during the day (active) period. However, nocturnal (night-time or passive) blood pressure is superior to daytime blood pressure in predicting cardiovascular risks. Therefore, night-time blood pressure measurements have to be also considered. So patients with office readings above than or equal to 140/90 mmHg and a mean ambulatory blood pressure below 130/80 mmHg have to be included as well.
The prevalence of white-coat hypertension in the community is around 20-25 percent.
What is White-Coat Effect?
The white-coat effect is defined as the increase in blood pressure during the office visit regardless of the daytime ambulatory blood pressure monitoring level or whether the patient receives or not antyhypertensive treatment. White-coat effect is present if the patient's office blood pressure is considerable higher than his or her daytime ambulatory blood pressure level.
So, while in case of white-coat hypertension the office blood pressure is high, but normal daytime ambulatory blood pressure levels are normal, patients with white-coat effect has high office blood pressure regardless of their daytime ambulatory blood pressure levels, which can also be raised above normal.
Ambulatory blood pressure monitoring can make a difference between the two phenomena, while an office blood pressure meter can only see patients with severe hypertension, even if the patients do not have hypertension at all, or if they develop only moderate hypertension at home.
Source: Eoin O'Brien, Gianfranco Prati, George Stergiou: Ambulatory Blood Pressure Measurement - What is the International Consensus? Click here for the review.