Diagnostic Approach to White Coat Effect and White Coat Hypertension

Abstract

An accurate measurement of blood pressure (BP) levels has important implications for clinical decision making, as it is the basis for a reliable diagnosis of hypertension and for assessment of BP control in treated subjects. The BP rise associated with the alerting reaction during the medical visit, the so-called white coat effect (WCE), represents a major problem associated with conventional BP measurement as it may lead to overestimation of initial BP levels in the absence of treatment and/or to underestimation of the effect of antihypertensive drugs in treated subjects. As a consequence of this, there will be a significant number of subjects with elevated BP levels in the office but with persistently normal out-of-office BP levels (a condition defined as “white coat” hypertension, WCH, or “isolated office” hypertension). Likewise, a considerable number of treated subjects will have apparent resistant hypertension in the office, despite achieving adequate out-of-office BP control with antihypertensive drugs (a condition defined as white coat resistant hypertension, WCRH). From a practical standpoint, the quantification of the magnitude of the WCE would allow estimating subjects’ actual BP levels, thus reducing misclassification of hypertension and providing a better assessment of BP control. However, an accurate and direct estimation of the WCE requires implementation of complex and sophisticated BP measurement techniques (i.e., beat-to-beat BP recordings) before, during, and after the medical visit [1, 2] which prevents it to be obtained routinely either in a clinical setting or in population studies. To overcome these difficulties, alternative, indirect approaches for estimation of the alarm reaction to the medical visit, based on discontinuous ambulatory BP recordings, have been proposed. The most popular of these indirect methods for the assessment of the WCE consists in the straightforward estimation of the difference between clinic BP and average daytime ambulatory BP levels (measured either with ambulatory or home BP monitoring) [3, 4]. By using this methodology, it is also possible to identify WCH (elevated in-office but normal out-of-office blood pressure levels) as well as WCRH (apparent resistant hypertension based on the finding of persisting elevated OBP measures accompanied by adequate control of out-of-office BP levels) in treated subjects. Since both of these conditions occur with a relatively high frequency in clinical practice, current hypertension guidelines [5, 6] have included suspicion of WCH in untreated patients among the clinical indications for out-of-office BP monitoring. Along the same line, guidelines for the management of resistant hypertension request as a mandatory step the exclusion of WCRH by means of a 24-h ambulatory BP monitoring, before proceeding with any interventional therapy of this condition [7].