- Email: [email protected]
Automated office blood pressure—the preferred method for recording blood pressure
Journal of the American Society of Hypertension
-(-)
(2016) 1–3
Controversies in Hypertension
Automated office blood pressure—the preferred method for recording blood pressure Martin G. Myers, MD, FRCPC* Schulich Heart Program, Division of Cardiology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; and Department of Medicine, University of Toronto, Toronto, ON, Canada
See related article on page XXX.
Why Manual Blood Pressure is no Longer Recommended for Diagnosing or Managing Hypertension During the 20th century, the mercury sphygmomanometer was widely recognized as the best method for measuring blood pressure (BP) with every major clinical trial in hypertension using this device. Detailed guidelines were established for the proper recording of BP with the mercury sphygmomanometer. Readings taken using these guidelines were considered to be the ‘‘gold standard’’ for determining an individual’s BP status. Today, manual BP measurement is no longer the method of choice for diagnosing hypertension. There are several reasons for changes in the guidelines and for the rapid decline in the use of the mercury sphygmomanometer. First, mercury has been banned from the workplace in most of the world because it is now considered to be an environmental hazard. Mercury was banned in Europe in 2009, and in 2013, the United Nations Minamata Convention on Mercury ratified a proposal which forbids the manufacture, import, and export of devices using mercury, including mercury sphygmomanometers (http://www. mercuryconvention.org). Although mercury devices may still be found in many doctors’ examining rooms in the United States, such is not the case in hospitals and other larger health-care centers. Instead, aneroid or electronic sphygmomanometers are being used, with other aspects of BP measurement remaining the same. Aneroid devices have different problems in that they contain mechanical components which malfunction with repeated use. Consequently, these devices require frequent recalibration which is often not done in clinical practice. *Corresponding author: Martin G. Myers, MD, FRCPC, Division of Cardiology, Sunnybrook Health Sciences, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada. Tel: þ1 4164804927. E-mail: [email protected]
Second, numerous studies have shown 24-hour ambulatory BP monitoring (ABPM) to be significantly better than manual BP in predicting future cardiovascular risk in relation to BP. Recent evidence-based guidelines such as National Institute for Health and Clinical Excellence (NICE) in the United Kingdom1 and the Preventive Services Task Force in the United States2 have recommended that ABPM should be used whenever possible to diagnose hypertension. In other words, 24-hour ABPM has now replaced the mercury sphygmomanometer as the gold standard for determining a patient’s BP status. Finally, studies conducted in ‘‘real-life’’ clinical practice have conclusively demonstrated that a manual BP reading recorded in a research study in accordance with recognized guidelines is not the same as a manual BP done in routine clinical practice.3 This finding was slow to be recognized because it is extremely difficult to conduct research in a ‘‘real-life’’ setting without participation in the study affecting the behavior of the medical staff and patients, a phenomenon known as the ‘‘Hawthorne Effect.’’ In every single study in which BP has been recorded in usual clinical practice, the readings were significantly higher than special readings obtained according to the standard guidelines for BP measurement (Table 1). Overall, the mean routine BP was 10/7 mm Hg higher than the BP recorded according to guidelines. It should be noted that the poor quality of usual manual office BP readings exists despite numerous efforts over many years to educate medical staff on the proper technique for recording manual BP. This difference between real-life and research BP readings has important implications for the diagnosis and management of hypertension. Instead of 140/90 mm Hg, the true cut-point for defining a normal BP in the office is closer to 150/95 mm Hg, unless the medical staff adhere to the established guidelines for proper BP measurement including 5 minutes of rest, no conversation, and no digit preference (rounding readings off to the nearest zero value). Evidence from research studies in the United States, Canada, and Australia tells us that this is frequently not done
1933-1711/$ - see front matter Ó 2016 American Society of Hypertension. All rights reserved. http://dx.doi.org/10.1016/j.jash.2016.01.007
M.G. Myers / Journal of the American Society of Hypertension
2
Table 1 Mean BP readings (mm Hg) recorded by patient’s own physician in usual clinical practice and as part of a research study (refer article by Myers3 for citations of studies)
Myers (1995) Brown (2001) Graves (2003) Gustavsen (2003) Myers (2009) Head (2010) Burgess (2011) Mean BP
No. of Patients
Usual Clinical Practice
Research Study BP
147 611 104 420 309 6817 150
146/87 161/95 152/84 165/104 152/87 150/89 145/85 153/90
140/83 152/85 138/74 156/100 140/80 142/82 132/79 143/83
BP, blood pressure.
(Table 1). As a consequence, there would seem to be two choices for the future of office BP measurement: continue using manual BP and change the cut-point for diagnosing hypertension to 150/95 mm Hg or change how BP is measured. However, if one takes into account the other important factors affecting office BP, the disappearance of the mercury sphygmomanometer and the shift to 24-hour ABPM for diagnosing hypertension, the best option would seem to be a change in how office BP is measured.
Semi-automated Electronic Sphygmomanometers for the Office One alternative is to use an electronic sphygmomanometer, with several types now available for office practice. Some devices have been specifically designed for professional use, whereas others (eg, Omron HEM-705) have been adapted from recorders originally intended for selfmeasurement of BP by patients in the home. These semiautomated devices have one feature in common in that they all require involvement of both the medical staff and patient to obtain a BP reading. It is this ‘‘human aspect’’ of BP measurement which still has the potential to promote a white coat effect and to reduce the accuracy of the readings.3 If the only difference between manual and electronic BP measurement is the device being used to record BP, then the other factors which adversely affect the BP reading are still present. Examples include not having the patient rest for 5 minutes before taking the BP readings, conversation between the patient and medical staff and recording only a single reading. Any of these deviations from the guidelines would tend to increase the likelihood of a misdiagnosis of hypertension. Even when the patient activates the device, the resulting BP readings are still subject to some white coat effect.4
Automated Office Blood Pressure By now it should be evident that the human factor in BP measurement must be reduced to a minimum to obtain an
-(-)
(2016) 1–3
accurate estimate of an individual’s BP status. It is not a coincidence that 24-hour ABPM records BP with the least involvement of a human (patient or medical staff) and is also the best method for determining an individual’s BP status. Advances in sphygmomanometer technology have now made it possible to record office BP with minimal human involvement. For more than a decade, it has been possible to record multiple BP readings using a fully automated sphygmomanometer with the patient resting quietly and alone,5 a technique now known as ‘‘automated office BP’’ (AOBP). Devices currently available for performing AOBP include the BpTRU, Omron HEM-907, and Microlife WatchBP Office (Welch Allyn PRO BP 2400).5 These devices require between 4 and 7 minutes to obtain a mean AOBP reading. Critics of the AOBP technique claim that this time is too long for recording BP in clinical practice. However, AOBP takes no longer than a proper manual BP recorded in duplicate after 5 minutes of rest, as recommended in the guidelines. Initial research using AOBP required the patient to be alone in an examining room. However, more recent studies4 have reported that AOBP can be performed in other locations such as the waiting room in a physician’s office, a pharmacy or an ABPM unit, provided that the patient is seated alone and is not disturbed. These findings are a response to critics of AOBP who say that requiring the patient to be alone for 4 to 7 minutes for an AOBP is impractical, although they seem to forget the need to have the patient resting quietly alone for 5 minutes before a proper manual BP reading is recorded in duplicate.
Specific Advantages of AOBP AOBP has a number of distinct advantages over usual office BP measurement provided that multiple readings are taken using a fully automated sphygmomanometer with the patient resting quietly and alone. AOBP has the same cut-point as home BP and awake ambulatory BP (135/85 mmHg) for defining hypertension.5,6 AOBP is more accurate than usual office BP, AOBP is not associated with the white coat effect seen with manual office BP and it is less subject to digit preference.5,6 AOBP also records multiple readings which is important in patients who have co-existing atrial fibrillation. Studies in a variety of patient populations3 including residents in the community and patients referred for 24-hour ABPM have reported that the mean AOBP was similar to the mean awake ambulatory BP and/or home BP. In several studies, awake ambulatory BP exhibited a significantly stronger correlation with AOBP than with manual office BP. AOBP and awake ambulatory both correlated significantly with left ventricular mass, a measure of target organ
M.G. Myers / Journal of the American Society of Hypertension
damage related to BP, whereas usual office correlated poorly.3 The threshold for defining hypertension using AOBP (135/85 mm Hg) has recently been confirmed in a clinical outcome study4 involving 3127 subjects followed for 4.9 years for the occurrence of nonfatal and fatal cardiovascular events. The only study (Community Health Awareness Program) to show that screening for hypertension can reduce hospitalization for cardiac diagnoses used AOBP to determine the subject’s BP status.2 The Systolic Blood Pressure Intervention Trial which reported that a target systolic BP < 120 mm Hg was associated with fewer cardiovascular events than the conventional target of <140 mm Hg used AOBP to diagnose and manage hypertension.7
AOBP and the Guidelines In 2011, the Canadian Hypertension Education Program recommended AOBP for the diagnosis of hypertension.8 Based on the evidence outlined previously described, the guidelines for 2016 will now recommend that AOBP be the preferred method for office BP measurement with manual BP no longer being recommended. In 2013, the European Society of Hypertension and European Society of Cardiology recommended using AOBP, if feasible.4 Considering the overwhelming evidence that AOBP is superior to manual office BP for diagnosing and managing hypertension, it is now time to use electronic sphygmomanometers which record multiple readings automatically with the patient resting quietly and alone in the office setting.
-(-)
(2016) 1–3
3
References 1. National Institute for Health and Clinical Excellence. Hypertension NICE Clinical Guidelines 127. London, UK: National Clinical Guidelines Centre; 2011. 2. Piper M, Evans CV, Burda BU, Margolis KL, O’Connor E, Whitlock EP. Diagnostic and predictive accuracy of blood pressure screening methods with consideration of rescreening intervals: a systematic review for the U.S. Preventative Services Task Force. Ann Intern Med 2015;162:192–204. 3. Myers MG. The great myth of office blood pressure measurement. J Hypertens 2012;30:1894–8. 4. Myers MG, Kaczorowski J, Paterson JM, Dolovich L, Tu K. Thresholds for diagnosing hypertension based upon automated office blood pressure measurements and cardiovascular risk. Hypertension 2015;66:489–95. 5. Myers MG, Godwin M, Dawes M, Kiss A, Tobe SW, Kaczorowski J. Measurement of blood pressure in the office—recognizing the problem and proposing the solution. Hypertension 2010;55:195–200. 6. Myers MG, Godwin M. Automated office blood pressure. Can J Cardiol 2012;28:341–6. 7. The SPRINT Research Group. A randomized trial of intensive versus standard blood pressure control. N Engl J Med 2015;373:2103–16. 8. Rabi DM, Daskalopoulou SS, Padwal RS, Khan NA, Grover SA, Hackam DG, et al. The 2011 Canadian Hypertension Education Program recommendations for the management of hypertension: blood pressure measurement, diagnosis, assessment of risk and therapy. Can J Cardiol 2011;27:415–33.
-(-)
(2016) 1–3
Controversies in Hypertension
Automated office blood pressure—the preferred method for recording blood pressure Martin G. Myers, MD, FRCPC* Schulich Heart Program, Division of Cardiology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; and Department of Medicine, University of Toronto, Toronto, ON, Canada
See related article on page XXX.
Why Manual Blood Pressure is no Longer Recommended for Diagnosing or Managing Hypertension During the 20th century, the mercury sphygmomanometer was widely recognized as the best method for measuring blood pressure (BP) with every major clinical trial in hypertension using this device. Detailed guidelines were established for the proper recording of BP with the mercury sphygmomanometer. Readings taken using these guidelines were considered to be the ‘‘gold standard’’ for determining an individual’s BP status. Today, manual BP measurement is no longer the method of choice for diagnosing hypertension. There are several reasons for changes in the guidelines and for the rapid decline in the use of the mercury sphygmomanometer. First, mercury has been banned from the workplace in most of the world because it is now considered to be an environmental hazard. Mercury was banned in Europe in 2009, and in 2013, the United Nations Minamata Convention on Mercury ratified a proposal which forbids the manufacture, import, and export of devices using mercury, including mercury sphygmomanometers (http://www. mercuryconvention.org). Although mercury devices may still be found in many doctors’ examining rooms in the United States, such is not the case in hospitals and other larger health-care centers. Instead, aneroid or electronic sphygmomanometers are being used, with other aspects of BP measurement remaining the same. Aneroid devices have different problems in that they contain mechanical components which malfunction with repeated use. Consequently, these devices require frequent recalibration which is often not done in clinical practice. *Corresponding author: Martin G. Myers, MD, FRCPC, Division of Cardiology, Sunnybrook Health Sciences, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada. Tel: þ1 4164804927. E-mail: [email protected]
Second, numerous studies have shown 24-hour ambulatory BP monitoring (ABPM) to be significantly better than manual BP in predicting future cardiovascular risk in relation to BP. Recent evidence-based guidelines such as National Institute for Health and Clinical Excellence (NICE) in the United Kingdom1 and the Preventive Services Task Force in the United States2 have recommended that ABPM should be used whenever possible to diagnose hypertension. In other words, 24-hour ABPM has now replaced the mercury sphygmomanometer as the gold standard for determining a patient’s BP status. Finally, studies conducted in ‘‘real-life’’ clinical practice have conclusively demonstrated that a manual BP reading recorded in a research study in accordance with recognized guidelines is not the same as a manual BP done in routine clinical practice.3 This finding was slow to be recognized because it is extremely difficult to conduct research in a ‘‘real-life’’ setting without participation in the study affecting the behavior of the medical staff and patients, a phenomenon known as the ‘‘Hawthorne Effect.’’ In every single study in which BP has been recorded in usual clinical practice, the readings were significantly higher than special readings obtained according to the standard guidelines for BP measurement (Table 1). Overall, the mean routine BP was 10/7 mm Hg higher than the BP recorded according to guidelines. It should be noted that the poor quality of usual manual office BP readings exists despite numerous efforts over many years to educate medical staff on the proper technique for recording manual BP. This difference between real-life and research BP readings has important implications for the diagnosis and management of hypertension. Instead of 140/90 mm Hg, the true cut-point for defining a normal BP in the office is closer to 150/95 mm Hg, unless the medical staff adhere to the established guidelines for proper BP measurement including 5 minutes of rest, no conversation, and no digit preference (rounding readings off to the nearest zero value). Evidence from research studies in the United States, Canada, and Australia tells us that this is frequently not done
1933-1711/$ - see front matter Ó 2016 American Society of Hypertension. All rights reserved. http://dx.doi.org/10.1016/j.jash.2016.01.007
M.G. Myers / Journal of the American Society of Hypertension
2
Table 1 Mean BP readings (mm Hg) recorded by patient’s own physician in usual clinical practice and as part of a research study (refer article by Myers3 for citations of studies)
Myers (1995) Brown (2001) Graves (2003) Gustavsen (2003) Myers (2009) Head (2010) Burgess (2011) Mean BP
No. of Patients
Usual Clinical Practice
Research Study BP
147 611 104 420 309 6817 150
146/87 161/95 152/84 165/104 152/87 150/89 145/85 153/90
140/83 152/85 138/74 156/100 140/80 142/82 132/79 143/83
BP, blood pressure.
(Table 1). As a consequence, there would seem to be two choices for the future of office BP measurement: continue using manual BP and change the cut-point for diagnosing hypertension to 150/95 mm Hg or change how BP is measured. However, if one takes into account the other important factors affecting office BP, the disappearance of the mercury sphygmomanometer and the shift to 24-hour ABPM for diagnosing hypertension, the best option would seem to be a change in how office BP is measured.
Semi-automated Electronic Sphygmomanometers for the Office One alternative is to use an electronic sphygmomanometer, with several types now available for office practice. Some devices have been specifically designed for professional use, whereas others (eg, Omron HEM-705) have been adapted from recorders originally intended for selfmeasurement of BP by patients in the home. These semiautomated devices have one feature in common in that they all require involvement of both the medical staff and patient to obtain a BP reading. It is this ‘‘human aspect’’ of BP measurement which still has the potential to promote a white coat effect and to reduce the accuracy of the readings.3 If the only difference between manual and electronic BP measurement is the device being used to record BP, then the other factors which adversely affect the BP reading are still present. Examples include not having the patient rest for 5 minutes before taking the BP readings, conversation between the patient and medical staff and recording only a single reading. Any of these deviations from the guidelines would tend to increase the likelihood of a misdiagnosis of hypertension. Even when the patient activates the device, the resulting BP readings are still subject to some white coat effect.4
Automated Office Blood Pressure By now it should be evident that the human factor in BP measurement must be reduced to a minimum to obtain an
-(-)
(2016) 1–3
accurate estimate of an individual’s BP status. It is not a coincidence that 24-hour ABPM records BP with the least involvement of a human (patient or medical staff) and is also the best method for determining an individual’s BP status. Advances in sphygmomanometer technology have now made it possible to record office BP with minimal human involvement. For more than a decade, it has been possible to record multiple BP readings using a fully automated sphygmomanometer with the patient resting quietly and alone,5 a technique now known as ‘‘automated office BP’’ (AOBP). Devices currently available for performing AOBP include the BpTRU, Omron HEM-907, and Microlife WatchBP Office (Welch Allyn PRO BP 2400).5 These devices require between 4 and 7 minutes to obtain a mean AOBP reading. Critics of the AOBP technique claim that this time is too long for recording BP in clinical practice. However, AOBP takes no longer than a proper manual BP recorded in duplicate after 5 minutes of rest, as recommended in the guidelines. Initial research using AOBP required the patient to be alone in an examining room. However, more recent studies4 have reported that AOBP can be performed in other locations such as the waiting room in a physician’s office, a pharmacy or an ABPM unit, provided that the patient is seated alone and is not disturbed. These findings are a response to critics of AOBP who say that requiring the patient to be alone for 4 to 7 minutes for an AOBP is impractical, although they seem to forget the need to have the patient resting quietly alone for 5 minutes before a proper manual BP reading is recorded in duplicate.
Specific Advantages of AOBP AOBP has a number of distinct advantages over usual office BP measurement provided that multiple readings are taken using a fully automated sphygmomanometer with the patient resting quietly and alone. AOBP has the same cut-point as home BP and awake ambulatory BP (135/85 mmHg) for defining hypertension.5,6 AOBP is more accurate than usual office BP, AOBP is not associated with the white coat effect seen with manual office BP and it is less subject to digit preference.5,6 AOBP also records multiple readings which is important in patients who have co-existing atrial fibrillation. Studies in a variety of patient populations3 including residents in the community and patients referred for 24-hour ABPM have reported that the mean AOBP was similar to the mean awake ambulatory BP and/or home BP. In several studies, awake ambulatory BP exhibited a significantly stronger correlation with AOBP than with manual office BP. AOBP and awake ambulatory both correlated significantly with left ventricular mass, a measure of target organ
M.G. Myers / Journal of the American Society of Hypertension
damage related to BP, whereas usual office correlated poorly.3 The threshold for defining hypertension using AOBP (135/85 mm Hg) has recently been confirmed in a clinical outcome study4 involving 3127 subjects followed for 4.9 years for the occurrence of nonfatal and fatal cardiovascular events. The only study (Community Health Awareness Program) to show that screening for hypertension can reduce hospitalization for cardiac diagnoses used AOBP to determine the subject’s BP status.2 The Systolic Blood Pressure Intervention Trial which reported that a target systolic BP < 120 mm Hg was associated with fewer cardiovascular events than the conventional target of <140 mm Hg used AOBP to diagnose and manage hypertension.7
AOBP and the Guidelines In 2011, the Canadian Hypertension Education Program recommended AOBP for the diagnosis of hypertension.8 Based on the evidence outlined previously described, the guidelines for 2016 will now recommend that AOBP be the preferred method for office BP measurement with manual BP no longer being recommended. In 2013, the European Society of Hypertension and European Society of Cardiology recommended using AOBP, if feasible.4 Considering the overwhelming evidence that AOBP is superior to manual office BP for diagnosing and managing hypertension, it is now time to use electronic sphygmomanometers which record multiple readings automatically with the patient resting quietly and alone in the office setting.
-(-)
(2016) 1–3
3
References 1. National Institute for Health and Clinical Excellence. Hypertension NICE Clinical Guidelines 127. London, UK: National Clinical Guidelines Centre; 2011. 2. Piper M, Evans CV, Burda BU, Margolis KL, O’Connor E, Whitlock EP. Diagnostic and predictive accuracy of blood pressure screening methods with consideration of rescreening intervals: a systematic review for the U.S. Preventative Services Task Force. Ann Intern Med 2015;162:192–204. 3. Myers MG. The great myth of office blood pressure measurement. J Hypertens 2012;30:1894–8. 4. Myers MG, Kaczorowski J, Paterson JM, Dolovich L, Tu K. Thresholds for diagnosing hypertension based upon automated office blood pressure measurements and cardiovascular risk. Hypertension 2015;66:489–95. 5. Myers MG, Godwin M, Dawes M, Kiss A, Tobe SW, Kaczorowski J. Measurement of blood pressure in the office—recognizing the problem and proposing the solution. Hypertension 2010;55:195–200. 6. Myers MG, Godwin M. Automated office blood pressure. Can J Cardiol 2012;28:341–6. 7. The SPRINT Research Group. A randomized trial of intensive versus standard blood pressure control. N Engl J Med 2015;373:2103–16. 8. Rabi DM, Daskalopoulou SS, Padwal RS, Khan NA, Grover SA, Hackam DG, et al. The 2011 Canadian Hypertension Education Program recommendations for the management of hypertension: blood pressure measurement, diagnosis, assessment of risk and therapy. Can J Cardiol 2011;27:415–33.