OFFICE BLOOD PRESSURE: CORNERSTONE OF HYPERTENSION MANAGEMENT
For almost a century the measurement of blood pressure (BP) in the office or clinic by the doctor or nurse using a standard mercury sphygmomanometer combined with the auscultatory method has been the standard approach to hypertension diagnosis and management . The vast majority of trials that demonstrated the risks associated with elevated BP and the benefits of treatment-induced BP reduction have used conventional office BP measurements. Although multiple outcome trials including thousands of individuals have consistently shown office BP to be a strong predictor of risk, in the individual patient, office BP has less prognostic value . The main drawbacks of office BP are due to operator (doctor or nurse)-related problems, such as observer's prejudice and bias (expectations), reading errors (terminal digit preference, rounding and random error) and the so-called ‘white-coat’ and ‘masked hypertension’ phenomena [1,2]. Moreover, it is acknowledged that in clinical practice, office BP measurements are less standardized than in clinical trials and might be misleading in a considerable proportion of patients [1,3–6]. Recently, the conventional office BP measurements have entered a period of fundamental change, which is not only dictated by the need for more reliable measures, but is also due to the demise of the mercury sphygmomanometer and to the recent development of accurate electronic BP monitors for professional use [3–13].
THE CONCEPT OF AUTOMATED OFFICE BP MEASUREMENT
Aiming to improve the accuracy of office BP measurement Myers et al.[3,4] introduced the concept of automated office BP measurement (AOBP). AOBP is characterized by the following specific features: (i) office BP measurements are taken while the patient is alone in the examination room; (ii) a professional automated oscillometric device is used; (iii) multiple BP measurements are taken (usually six) within 15–30 min; (iv) the first measurement is discarded. The obvious advantages of the AOBP method are related to the fact that measurements are taken in the absence of an observer, who is the main source of error with the conventional office BP measurement approach, and to the larger number of BP readings obtained as compared to the usual office BP measurement.
In this issue of the journal Myers et al.[3,4] present the rationale for introducing the AOBP measurement method and summarized the evidence obtained so far supporting the clinical usefulness of the method. A strategy for the diagnosis of hypertension based on AOBP measurements is also proposed [3,4]. The main elements in favor of the AOBP method are its better reproducibility compared to the conventional office BP measurements, as well as its closer association with ambulatory BP and indices of preclinical organ damage [3,4].
Although there is a clear need to improve the reliability of office BP measurement, and, in spite of the fact that, indeed, the AOBP method seems to represent an interesting and ‘better’ solution in this context, there are several issues to be considered regarding its application that remain inadequately investigated, unresolved, or ignored.
- The features of the AOBP measurement method (multiple measurements, exclusion of first measurement, absence of physician) result in lower BP readings as compared to the usual office BP [3,4]. Therefore, quite rightly the investigators had to define a lower BP threshold for hypertension diagnosis based on AOBP [3,4]. However, defining the normality threshold for a given BP measurement method takes a lot more than correspondence criteria based on measurements taken by another method as performed by Myers et al. Further studies are required to identify AOBP normalcy levels, as well as the threshold for hypertension diagnosis based on outcome data, by examining the ability of AOBP to predict morbidity and mortality, as previously performed for other measurement methods, such as office, ambulatory and home BP measurements [1,14].
- It is important to mention that Myers et al. in their proposed strategy for hypertension diagnosis based on AOBP acknowledged that in patients with high-normal office BP (130–139 mmHg SBP and 80–89 mmHg DBP) assessment of out-of-office BP using ambulatory or home BP monitoring would be required for a precise diagnosis to be made. Given the Gaussian distribution of BP in the general population that peaks close to 130 mmHg SBP and 80 mmHg DBP, the proportion of individuals who will require out-of-office BP monitoring on top of the use of the AOBP method is thus enormous. Indeed, in 2011 the National Institute for Health and Clinical Excellence (NICE) in the United Kingdom recommended that ambulatory BP monitoring should be offered to all people suspected of having hypertension . However, self-home BP monitoring will probably take over most of this task, because of its wider availability, lower cost and better acceptance by patients as compared to ambulatory BP monitoring .
- Another issue is the quality of AOBP measurements when routinely applied in general practice. Even if the AOBP trials attempted to mimic how AOBP is actually applied in clinical practice, this method was more standardized (same device and measurement protocol) than the ‘usual’ office BP with which it was compared (different devices and measurement protocols). Moreover, a ‘research study’ effect might have influenced the performance of doctors in BP measurement.
- The major and yet unresolved issue, however, is whether the measurement of BP in the office can be exclusively based on automated oscillometric devices.
SHOULD THE ASSESSMENT OF OFFICE BP BE EXCLUSIVELY BASED ON AUTOMATED OSCILLOMETRIC DEVICES?
The proposal by Myers et al. to make BP measurements in the office exclusively using automated electronic devices has been a matter of debate in the last decade [5,6,8–13]. Although as mentioned above, there are several advantages of replacing the auscultatory devices with electronic ones; there are at least three important reasons why at the present time auscultatory devices should remain available in the office.
- The oscillometric devices do not yield accurate BP measurements in a considerable proportion of individuals for reasons that remain unclear and might be related with arterial stiffness and pulse pressure or other hemodynamic parameters [16,17].
- In the presence of arrhythmia – particularly atrial fibrillation – the oscillometric devices are not accurate. A recent review and meta-analysis of studies that validated electronic devices in patients with sustained atrial fibrillation showed consistent overestimation of DBP . Moreover, asymptomatic arrhythmias might be missed in a follow-up office visit, as the automated device will display a BP reading despite the presence of arrhythmia, and the radial artery might not be palpated by the doctor or nurse.
- The evaluation of the accuracy of the oscillometric devices does not require only service (as in the case of mercury sphygmomanometers) or metrological calibration (as required with aneroid devices), but clinical validation against a mercury sphygmomanometer using one of the established protocols [19–21]. More importantly, an oscillometric device that has been successfully validated in adults may not be accurate in specific populations (e.g. elderly, diabetics, pregnancy, obese, children, end-stage renal disease). Therefore, separate validation is required in these subgroups of patients [1,19–21].
EUROPEAN RECOMMENDATIONS FOR OFFICE BP MEASUREMENT
In 2009, the European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) recommended that due to environmental issues the mercury sphygmomanometers should be banned from clinical use and remain available only for clinical validation studies as reference standard for alternative mercury-free BP measurement devices, until an alternative standard is developed and recognized . Thus, the current status is that mercury sphygmomanometers are not, or will not be available in the near future, and reliable mercury-free alternatives should be used.
In 2012, the European Society of Hypertension Working Group on Blood Pressure Monitoring in a position article questioned the exclusive use of oscillometric devices for office/clinic BP measurement and suggested that, at the present time, it is premature to abandon the auscultatory technique altogether . Due to the above mentioned issues of the oscillometric devices a recommendation was given that validated professional oscillometric BP monitors can be used, yet mercury-free devices that use the auscultatory method (aneroid or hybrid devices with liquid crystal display [LCD], light emitting diode [LED] or digital screen) should also be available in the office or clinic . Alternatively, devices with dual measurement mode (oscillometric and auscultatory) might be used to allow the physician to select the preferred method in each individual (e.g. auscultation in arrhythmia) . Particularly for children, the 2009 European Society of Hypertension Guidelines for pediatric hypertension recommended that elevated BP detected in children by oscillometric devices should be confirmed by auscultatory BP measurement .
In conclusion, despite the fact that the automated oscillometric devices have dominated the ambulatory and self-home BP monitoring market, their use as the only method for BP measurement in the office is still debatable . Due to technical issues of the oscillometric technique, at present it is premature to abandon the auscultatory technique altogether . Thus, although the present trend favors replacing the mercury sphygmomanometer with automated oscillometric devices, the auscultatory technique with the mercury component replaced by other validated mercury-free technologies should also be available in the office for the measurement of BP in cases where the oscillometric method is likely to be inaccurate .
Source of funding: None.
Conflicts of interest
There are no conflicts of interest.
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