White coat hypertension and white coat effect: its relevance to family physicians

Samuel Y S Wong 黃仰山

HK Pract 2007;29:409-410

"White coat hypertension" is an important clinical problem in general/family practice. It affects a considerable proportion of hypertensives¹ despite variation in the prevalence of the condition. Although there is some controversy about this issue, most investigators have found that white coat hypertension diagnosed by ambulatory blood pressure monitoring (ABPM) is not associated with increased morbidity and thus usually does not require drug treatment.^2,3

Ambulatory blood pressure monitoring and home monitoring are two methods that are commonly used to diagnose "white coat hypertension" and evidence shows that both can improve the management of hypertension.^4,5 In a literature review, Appel and Stason⁶ showed that end organ damage correlated much better with ambulatory blood pressure readings than with office readings and within the office, readings by physicians were higher than readings by nurse or technicians.

Research conducted to study the predictors of the white coat effect or white coat hypertension in general/family practice patients is important because ambulatory blood pressure monitoring can be costly and identification of predictors for white coat hypertension or white coat effect can help family physicians identify those who can obtain the most benefits from ABPM, making ABPM more cost effective⁷. Moreover, unnecessary side effects and costs can be reduced in those patients with only white coat hypertension.

Previous overseas studies^7,8 demonstrated a number of predictors of white coat hypertension in primary care. These included blood pressure readings, gender, body mass index, smoking status and small left ventricular mass although the findings were not consistent.

In this issue of the Hong Kong Practitioner, Tam et al⁹, in a retrospective study, provided further evidence in the predictors of white coat hypertension in our Chinese primary care population. Although the study design was retrospective, it provided important information for predictors of white coat hypertension in patients with home monitoring of blood pressure.

Other important research in white coat hypertension, home monitoring or ambulatory monitoring of blood pressure included studies that look into the normal values for blood pressure taken at home and the more proper threshold for treatment of hypertension when the values of blood pressure from home monitoring is used. In the area of predictors of white coat hypertension, further prospective studies will provide family physicians with important practical information for identification of patient characteristics that can help in the identification of family practice patients that can most benefit from ABPM.