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Self-measurement of blood pressure in the office and at home

Myers, Martin Ga; Parati, Gianfrancob

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Measurement of blood pressure depends upon a variety of factors, including how the reading is taken, which device is used and where the recording is performed [1]. At opposite poles are routine office readings taken by physicians and the 24-h ambulatory blood pressure recorded during usual daily activities. Numerous studies [1–4] have shown the former to be a relatively poor predictor of clinical outcome, particularly when a few isolated readings are considered, and more likely to provoke a white-coat effect, whereas the latter has been demonstrated in most cases to be superior in defining hypertension and cardiovascular risk. The value of home or self blood pressure measurement in clinical practice is less clear.

Self-measurement of blood pressure by the patient is intuitively attractive in that it presents an opportunity to reduce some of the white-coat effect experienced by many patients in the office setting without having to deal with the expense and complexity of ambulatory blood pressure monitoring. Evidence is available demonstrating that it is the presence of a physician, and not the cuff inflation itself, that induces the alerting reaction in the patient defined as the ‘white-coat effect’ [5], and this finding supports the use of automated measurements in this setting. Outcome studies, mainly utilizing left ventricular mass as a surrogate endpoint, have shown that self-measurement of blood pressure in the home is a more predictive value than routine office blood pressure, but is not as good as the 24-h ambulatory blood pressure [6].

However, the evidence available on this issue is still limited, and additional studies are currently in progress in this field. It would not be surprising if the results obtained further emphasize the clinical relevance of self blood pressure measurement at home, given the many positive features that characterize blood pressure readings obtained in this setting [6]. Among them is the possibility of obtaining multiple readings over periods of weeks and months, the average of which has been shown to be highly reproducible and little affected by placebo or white-coat effects. Moreover, by actively involving the patient in the management of his/her hypertensive status, a higher compliance with the prescribed treatment regimen may be expected. However, a few technical features must be considered for a proper interpretation of self-measured blood pressure values, including the type of device selected and the environmental conditions in which the measurements are taken.

In this issue of the journal, Stergiou et al. [7] address several methodological aspects of self-measurement of blood pressure, including comparisons between self blood pressure and physician readings in the office, or between self-measurement and blood pressure measured by a relative in the home. In addition, they discuss the proper term for describing self-measurement of blood pressure outside of an office setting.

The routine office blood pressure taken by a physician tends to provoke the greatest white-coat effect in susceptible patients. When the same physician measures blood pressure under ‘research’ conditions, almost one-half of the white-coat effect can be eliminated compared to readings taken in routine clinical practice [8]. Can the white-coat effect be diminished further by having patients record their own blood pressure in the doctor's office without anyone else being present in the examining room? According to Stergiou et al. [8], the answer would appear to be negative.

These authors reported no significant difference between self- and physician-measured blood pressure in the clinic. Their findings are virtually identical to an earlier study [9] in which self-recorded blood pressure values in treated hypertensive patients were no different from readings taken by their own family doctors during routine visits to the office.

A problem common to both these and other similar studies is the role of the so-called ‘Hawthorne effect’ [10] in which the behaviour of the physician changes when participating in a research study, with more care being taken in the measurement of blood pressure compared to routine clinical practice. Indeed, an earlier study [8] demonstrated the prevalence of a white-coat effect decreasing from 62 to 37% when the patient's own family doctor recorded blood pressure as part of a research study compared to routine readings taken by the same person in the office before involvement in the study.

Thus, self-measured blood pressure readings in the office are likely to be similar to readings taken by a physician under research conditions. However, the self-measured office blood pressure is very likely to be lower than the routine physician reading [8].

To date, there are few data on the use of self-measured blood pressure in the office in patients who have been identified as having a pronounced white-coat effect. To assess the potential value of automated self-measurement of blood pressure in the office, it would be important to investigate whether this approach can be used to reduce the white-coat response experienced by these individuals, who may not necessarily have been well represented in the patient population of Stergiou et al. [8] or in other studies.

The question of who should record blood pressure in the home using an automated device appears to have been answered by Stergiou et al. [8]. Home readings taken by self versus a relative were almost identical, with both being lower than the corresponding office values. Thus, there appears to be little reason to involve others in the measurement of blood pressure in the home unless patients are incapable of taking readings on their own.

Furthermore, based on the results of this study, another issue is whether we should use the terms ‘self’ or ‘home’ blood pressure to designate readings taken by patients at home. Stergiou et al. [8] propose that we use ‘home’ because self-readings and those taken taken by others in a home setting were similar, whereas self-measurements taken in the doctor's office were similar to those measured by the physician and higher than those obtained at home.

However, there are other reasons why more information is required regarding the circumstances of blood pressure measurement than that carried by the use of terms such as ‘home’ or ‘self’ readings.

Self-measurement of blood pressure can occur in places other than the home, including at the worksite and in the community (e.g. the local pharmacy). Different settings may give different readings, especially if a non-validated device is used, such as has been the case with readings taken in the community [11]. To assess the clinical importance of blood pressure measurements, information on how and where the readings were taken should therefore be available (Table 1). Only then will it be possible to assess an individual's true blood pressure status with confidence.

Table 1:
List of the specific features of blood pressure recordings performed in various settings for which information should be available for a proper clinical interpretation of the blood pressure values obtained


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© 2003 Lippincott Williams & Wilkins, Inc.