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Algorithms for diagnosing hypertension in the office: translating principle into practice

Myers, Martin Ga; Godwin, Marshallb

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doi: 10.1097/HJH.0b013e32832f343e
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Measurement of blood pressure (BP) in the office/clinic setting has been associated with a relatively high prevalence of white-coat hypertension. Efforts to improve the quality of manual BP readings in routine clinical practice have had little impact on this phenomenon despite widespread promotion of guidelines for proper measurement technique by national and international organizations. The net result has been a trend toward home and 24-h ambulatory BP monitoring (ABPM) in the diagnosis and management of hypertension.

In the current issue, Shimbo et al. [1] propose an algorithm which they believe could substantially reduce the reliance on out-of-office BP for the diagnosis of hypertension. The concept behind their approach is sound but sometimes the quality of research can be too good, which may be the case in this study.

The protocol involves high quality office BP measurements performed with strict adherence to American Heart Association guidelines. As a consequence, because of the type of participants recruited and ‘research quality’ BP recordings, the mean office BP was actually lower than the mean awake ambulatory BP. This approach left only 84 of 229 enrolled participants with a diagnosis of office hypertension.

One of the concerns about this study is the lack of information about participant recruitment and BP status. The authors evaluated 329 potential participants derived from patients attending two hospital hypertension centres and normal participants who replied to advertisements. It is not clear why only 229 of the 329 participants underwent home BP measurement. Similarly, there are no data on either the number of patients enrolled with a diagnosis of hypertension or the number of participants who were considered to be normotensive prior to performing the careful ‘research quality’ office BP readings. It would seem likely that many participants recruited with a diagnosis of hypertension were classified as normotensive on the basis of these readings. The remaining patients were then entered into an algorithm which demonstrated that those hypertensives with higher office BP readings did not benefit from further testing with 24-h ABPM.

The concept of the algorithm would seem to be sound. However, a problem arises when the findings are extended to diagnosing hypertension in routine clinical practice. The authors themselves caution that future research is needed before the algorithm can be used in an outpatient setting.

It is not surprising that a carefully performed manual office BP may reduce the need to perform 24-h ABPM. The problem is that physicians and other health professionals in the community generally do not adhere to established guidelines for manual BP measurement, leading to the well documented white-coat phenomenon in this setting. Because the proposed algorithm is based on a ‘research quality’ office BP, it would seem to be of little practical value for routine management of hypertension.

Nonetheless, there may be a solution to the disconnect between research and the ‘real-world’. Automated office BP (AOBP) with the patient alone in the examining room has been shown to eliminate the white-coat response in populations derived from the community [2] and among individuals referred for 24-h ABPM [3]. Mean AOBP readings are similar to the mean awake ambulatory BP, as were the BP readings in the study of Shimbo et al. [1], and correlate significantly better with the ambulatory BP than do routine manual BP readings taken in the offices of primary care physicians [2,3]. If the principles proposed by Shimbo et al. are reproducible in the ‘real-world’, AOBP measurement offers a possible approach to duplicating research quality BP in routine clinical practice.

In 146 untreated patients referred for 24-h ABPM [3], 55% had white-coat hypertension based on the routine manual office BP taken in the offices of their own family physicians with readings above 140/90 mmHg compared with mean awake ambulatory BP less than 135/85 mmHg. In contrast, only 16% patients had a diagnosis of white-coat hypertension with AOBP readings even though the cut-point for hypertension based on the AOBP was lower (135/85 mmHg) than for the manual BP readings.

Not only does AOBP eliminate the white-coat response, but readings also correlate better with the ambulatory BP than do routine manual BP readings [2,3]. AOBP is also more closely correlated with intima-media thickness of the carotid artery [4]. In an earlier study from one of our centres [5], more careful measurement of office BP by the patients' own family physicians correlated with left ventricular mass index the same as a ‘research quality’ BP taken by a study nurse and the mean awake ambulatory BP. However, a routine manual BP reading taken by the same physicians prior to their patients being enrolled in the study showed no significant correlation with left ventricular mass index.

Shimbo et al. [1] propose that ‘research quality’ office BP readings may preclude the need to perform ABPM in many patients with suspected hypertension. Even using lower cut-points for normotension/hypertension, AOBP would seem to accomplish the same goal. Indeed, data recently submitted for publication by one of the authors (M.G.M) shows that an algorithm for AOBP similar to the one used by Shimbo et al. is able to achieve the same results. Since, AOBP readings are similar when taken during routine office visits and during visits to an ABPM unit [6], the use of AOBP should achieve the goal of reducing the need for performing 24-h ABPM not only in a hypertension research study but also in clinical practice. About 10 000 BpTRU devices are currently in use for recording AOBP in Canada (M. Gelfer, BpTRU Medical Devices Ltd., Coquitlam, British Columbia, Canada) with some major ambulatory care centres in the United States also having abandoned mercury sphygmomanometers in favour of AOBP with devices, such as the BpTRU. Other devices for AOBP measurement, such as the Omron HEM 907 (Omron, Bannockburn, Illinois, USA) and Microlife WatchBP Office (Microlife, Widnau, Switzerland) are attracting more interest both for research and for routine use in clinical practice.

Some hypertensive experts [7,8] have recently advocated the abandonment of office BP measurement because of its poor correlation with cardiovascular risk, especially when dealing with the individual patient. Proponents of better training of health professionals in the community in order to achieve ‘research quality’ BP measurement seem to have had little impact on the quality of BP readings in routine clinical practice. AOBP offers an opportunity to rehabilitate the office BP by providing readings which are consistent from visit-to-visit and are highly correlated with the ambulatory BP, a gold standard for BP in evaluating the risk of target organ damage. As with ‘research quality’ office BP readings, in the study of Shimbo et al., the use of AOBP should reduce the need to obtain 24-h ABPM recordings, especially for the long-term management of hypertensive patients.

References

1 Shimbo D, Kuruvilla S, Haas D, Pickering TG, Schwartz JE, Gerin W. Preventing misdiagnosis of ambulatory hypertension: algorithm using office and home blood pressures. J Hypertens 2009; 27:1775–1783.
2 Beckett l, Godwin M. The BpTRU automatic blood pressure monitor compared to 24 h ambulatory blood pressure monitoring in the assessment of blood pressure in patients with hypertension. BMC Cardiovasc Disord 2005; 5:18.
3 Myers MG, Valdivieso M, Kiss A. Use of automated office blood pressure measurement to reduce the white-coat response. J Hypertens 2009; 27:280–286.
4 Campbell NRC, McKay DW, Conradson H, Lonn E, Title LM, Anderson T. Automated oscillometric blood pressure versus auscultatory blood pressure as a predictor of carotid intima-medial thickness in male fire fighters. J Hum Hypertens 2007; 21:588–590.
5 Myers MG, Oh PI, Reeves RA, Joyner CD. Prevalence of white coat effect in treated hypertensive patients in the community. Am J Hypertens 1995; 8:591–597.
6 Myers MG, Valdivieso M, Kiss A. Consistent relationship between automated office blood pressure recorded in different settings. Blood Press Monit 2009; 14:108–111.
7 O'Brien E. Ambulatory blood pressure measurement: the case for implementation in primary care. Hypertension 2008; 51:1435–1441.
8 Padfield PL. Measuring blood pressure: who and how? J Hypertens 2009; 27:216–218.
© 2009 Lippincott Williams & Wilkins, Inc.