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Automated blood pressure measurement may reduce impact of white coat effect on hypertension diagnosis, study finds

Wednesday, January 14 2009 | Comments

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What's This? The white coat effect on blood pressure (BP) may be a conditioned response that could potentially be addressed through the use of automated BP devices in office settings, according to findings from a recent study.

"The white coat effect (defined as the difference between BP measurements taken at the physician's office and those taken outside the office) is an important determinant of misdiagnosis of hypertension, but little is known about the mechanisms underlying this phenomenon," the authors of the study wrote.

To investigate the white coat effect and determine whether it may be a conditioned response, 238 patients in a hypertension clinical wore ambulatory BP monitors on 3 separate days 1 month apart. At each clinic visit, BP readings were manually triggered in the waiting area and the examination room--in the presence and absence of the physician--and were compared with the mercury sphygmomanometer readings taken by the physician in the examination room. Patients also completed trait and state anxiety measures before and after each BP assessment.

Overall, 35% of patients were normotensive, 9% had white coat hypertension, 37% had sustained hypertension, and 19% had masked hypertension.

Trait and state anxiety measures indicated that the white coat effect is a conditioned response "since the patients with white coat hypertension did not differ from the other groups in terms of the trait measures of anxiety but differed markedly in the levels of anxiety reported in the medical setting, with the greatest difference reported during the physician measurement," the authors wrote.

Using analysis of covariance, the interaction between setting (i.e., waiting room or examination room, physician absent or present) and the diagnostic category was statistically significant for both systolic (P<.001) and diastolic (P<.01) BP.

To further explore this interaction, the researchers examined BP changes among measurements taken just before the physician entered the room, those taken by the physician, and those taken just after the physician left the room. Controlling for age and sex, patients with white coat hypertension had significantly larger increases in both systolic (P<.001) and diastolic (P=.002) BP relative to patients from the other 3 BP diagnostic categories when the physician entered the room.

Likewise, patients with white coat hypertension had significantly larger decreases in systolic (P<.001) and diastolic (P=.001) BP relative to patients from the other 3 diagnostic categories when the physician exited the room.

"The results provide support for the hypothesis that anxiety and/or BP is a conditioned response to a specific set of stimuli, notably, the presence of the physician," the authors wrote. "We suggest that one way of addressing this problem is to modify the method by which BP is measured in the office setting given the wide availability of reliable and validated automated BP monitors that are suitable for both office and home use," they concluded. (Ogedegbe G, et al. Arch Intern Med 2008;168:2459-2465.)

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