White coat hypertension is a phenomenon in which patients exhibit elevated blood pressure in a clinical setting but not when recorded by themselves at home. It is believed that this is due to the anxiety some people experience during a clinic visit.
As the notion of "normal" is subjective and changes from individual to individual a reference measurement was necessary. As night-time and self measured values are often not subject to daily stress and clinical values are subject to unusual anxiety, daytime ambulatory blood pressure is used as a reference as it takes into account daily stress but not in excess. Due to specificity involved in diagnosis of white coat hypertension, many problems have been incurred in its diagnosis and treatment.
Patients of white coat hypertension do not exhibit the signs indicative of trepidation and their increased blood pressure is often not accompanied with tachycardia (TG Pickering 1988). This is supported by studies that repeatedly indicate that 15–30% of those thought to have mild hypertension as a result of clinic or office recordings, display normal blood pressure and no unusual response to pressure stimulus. These persons did not show any specific characteristics such as age that may be indicative of a higher susceptibility to white coat hypertension (BP McGrath, 1996).
Ambulatory blood pressure monitoring and patient self-measurement using a home blood pressure monitoring device is being increasingly used to differentiate those with white-coat hypertension or experiencing the white coat effect from those with chronic hypertension. This does not mean that these methods are without fault. Day time ambulatory values, despite taking into account stresses of everyday life when taken during the patient’s daily routine, is still susceptible to the effects of daily variables such as physical activity, stress and duration of sleep. Ambulatory monitoring has been found to be the more practical and reliable method in detecting patients with white coat hypertension and for the prediction of target organ damage. Even as such, the diagnosis and treatment of white coat hypertension remains controversial.
Recent studies (American Journal of Hypertension, May 2006) showed home blood pressure monitoring is as accurate as a 24 hour ambulatory monitoring in determining blood pressure levels. Researchers at the University of Turku, Finland studied 98 patients with untreated hypertension. They compared patients using a home blood pressure device and those wearing a 24hr ambulatory monitor. Researcher Dr. Niiranen said that, "home blood pressure measurement can be used effectively for guiding anti-hypertensive treatment". Dr. Stergiou added that home tracking of blood pressure, "is more convenient and also less costly than ambulatory monitoring".
It should be remembered that all the established published trials on the consequences of high blood pressure and the benefits of treating, are based on one-time measurement in clinical settings rather than the generally slightly lower readings obtained from ambulatory recordings.
The debate and conflicting ideas revolve around whether or not it would be feasible to treat white coat hypertension as there still is no conclusive evidence that a temporary rising in blood pressure during clinic visits has an adverse effect on health.
In fact many cross sectional studies have shown that "target-organ damage (as exemplified by left ventricular hypertrophy) is less in white-coat hypertensive [patients] than in sustained hypertensive [patients] even after the allowance has been made for differences in clinic pressure"(TG Pickering, 1994). Many believe that patients with "white coat" hypertension do not require even very small doses of antihypertensive therapy as it may result in hypotension but must still be careful as patients may show signs of vascular changes and may eventually develop hypertension.
If a typically normotensive patient has high blood pressure during an anxiety provoking experience, such as being reviewed by a health care professional, they are said to be experiencing the white coat effect.