Advertisement
Canadian Journal of Cardiology
Editorial| Volume 31, ISSUE 5, P583-584, May 2015

Download started.

Ok

Limitations of Home Blood Pressure Monitoring in Clinical Practice

  • Martin G. Myers
    Correspondence
    Corresponding author: Dr Martin G. Myers, Sunnybrook Health Sciences Centre, Suite A209d – 2075 Bayview Ave, Toronto, Ontario M4N 3M5, Canada.
    Affiliations
    Division of Cardiology, Schulich Heart Program, Sunnybrook Health Sciences Centre, and Department of Medicine, University of Toronto, Toronto, Ontario, Canada
    Search for articles by this author
Published:March 11, 2015DOI:https://doi.org/10.1016/j.cjca.2015.03.008
      Home blood pressure (BP) monitoring is recommended in the Canadian Hypertension Education Program (CHEP) guidelines as an alternative to 24-hour ambulatory BP monitoring (ABPM) for making a diagnosis of hypertension when ABPM is not feasible.
      • Daskalopoulou S.S.
      • Rabi D.M.
      • Zarnke K.B.
      • et al.
      The 2015 Canadian Hypertension Education Program recommendations for blood pressure measurement, diagnosis, assessment of risk, prevention, and treatment of hypertension.
      This recommendation is based on evidence from several population studies that showed that home BP is a significantly better predictor of future cardiovascular risk than manual office BP measurement.
      • Stergiou G.S.
      • Siontis K.C.
      • Ioannidis J.P.
      Home blood pressure as a cardiovascular outcome predictor.
      Home BP monitoring has gained immense popularity in recent years, for patients and for health professionals, no doubt in part because of recommendations from national and international organizations, such as CHEP.
      However, many devices are also purchased by individuals who are simply interested in knowing their BP without being told to do so by a health professional. Hypertension is one of the few conditions in which patients can directly participate in their care by generating BP readings which might determine whether medication is prescribed. Much has been written about the shortcomings of manual office BP measurement and how observer error and bias might adversely affect the accuracy and reliability of the readings, especially in actual clinical practice.
      • Myers M.G.
      The great myth of office blood pressure measurement.
      Such has not been the case with home BP readings. In this issue of the Canadian Journal of Cardiology, Milot et al.
      • Milot J.P.
      • Birnbaum L.
      • Larochelle P.
      • et al.
      Unreliability of home blood pressure measurement and the effect of a patient-oriented intervention.
      report on various aspects of home BP as seen from the patient's perspective. Their results provide a rare insight into home BP measurement in a ‘real world’ setting.
      There are specific guidelines on the proper procedures for home BP measurement
      • Daskalopoulou S.S.
      • Rabi D.M.
      • Zarnke K.B.
      • et al.
      The 2015 Canadian Hypertension Education Program recommendations for blood pressure measurement, diagnosis, assessment of risk, prevention, and treatment of hypertension.
      • Parati G.
      • Stergiou G.S.
      • Asmar R.
      • et al.
      European Society of Hypertension guidelines for blood pressure monitoring at home: a summary report of the Second International Consensus Conference on Home Blood Pressure Monitoring.
      with each step involving the participation of the patient who must first purchase a validated device with a proper sized cuff and must then be educated on how to record BP properly, either from information provided at the time of purchase or from sources such as the Hypertension Canada Web site. For example, multiple readings should be taken according to a specified schedule and not when the patient is especially relaxed, anxious, or upset. Recording BP during a headache might lead an individual to conclude that the BP is high enough to cause a stroke, when in reality the pain from the headache transiently increases the BP.
      The study by Milot et al.
      • Milot J.P.
      • Birnbaum L.
      • Larochelle P.
      • et al.
      Unreliability of home blood pressure measurement and the effect of a patient-oriented intervention.
      examined how closely patients who attended an academic hypertension clinic adhered to recommendations for proper home BP measurement. Data on compliance were obtained via a detailed questionnaire completed by 535 patients on 2 occasions, 4 years apart. The findings were limited by the data being self-reported which would tend to show adherence to the guidelines better than it actually was. Nonetheless, more than half of the patients said they recorded their home BP when they had symptoms and not according to a specified schedule as had been recommended. Less than 30 percent of patients said they had reported all of their readings to the doctor. Overall, about half of the patients claimed to follow 5 or all 6 of the most important procedures for proper home BP measurement at least 80% of the time.
      Because these self-reported data were part of a research study and were accompanied by an intensive educational program, it is very likely that the responses were subject to the Hawthorne effect,
      • Sedgwick P.
      The Hawthorne effect.
      with patients appearing to be more compliant with the recommended procedures for proper home BP measurement than actually was the case. The investigators concluded that the overall performance of the subjects was “suboptimal.” In reality, if one takes into account the circumstances under which the data were collected, adherence to protocols for home BP measurement in routine clinical practice is even worse than what was reported by Milot et al.
      • Milot J.P.
      • Birnbaum L.
      • Larochelle P.
      • et al.
      Unreliability of home blood pressure measurement and the effect of a patient-oriented intervention.
      Several items in the questionnaire which involve possible ‘reporting bias’ are of particular relevance to the use of home BP in diagnosing and treating hypertension. Subjects were asked about the percentage of BP readings they write down and how often they bring their BP records to the doctor. Because the information was self-reported by the patients, Milot et al were not able to verify how frequently accurate BP readings were actually reported to the doctor's office.
      The possibility of reporting bias affecting home BP was initially addressed in 2 studies conducted in routine clinical practice which were reported independently by Myers
      • Myers M.G.
      Self-measurement of blood pressure at home: the potential for reporting bias.
      and Mengden et al.
      • Mengden T.
      • Hernandez Medina R.M.
      • Beltran B.
      • et al.
      Reliability of reporting self-measurement of blood pressure values by hypertensive patients.
      in 1998. In virtually identical studies, these investigators compared home BP readings transmitted by patients in writing with the actual readings stored in the memory of the home BP recorder. The patients were unaware of the data storage feature of the devices and did not know they were participating in a research study. In both studies, the transcribed readings frequently did not match the readings which were actually taken, with some values being either higher or lower and other readings being factitious or missing altogether. These ‘real world’ findings were not subject to the Hawthorne effect, unlike the results of subsequent research studies on reporting bias
      • Myers M.G.
      • Stergiou G.S.
      Reporting bias: the Achilles heel of home blood pressure measurement.
      in which the patients were aware that their performance was being evaluated. Overall, the more subjects were aware that their reporting of home BP readings was being evaluated, the more accurately they transmitted the actual readings.
      Advances in technology have created potential solutions to the problem of reporting bias. Most devices now have the capacity to store readings, making it possible for the patient to bring the recorder to the office so that the doctor or nurse can verify the individual measurements and mean home BP value. However, these procedures have not been part of routine clinical practice with patients frequently encouraged to record their home BP readings on forms specifically designed for this purpose. When home BP readings are transcribed on to paper and then given to the physician, the possibility of reporting bias should be considered.
      Reliable transmission of all BP readings recorded by patients is now possible using telemonitoring systems that automatically send home BP readings using Bluetooth technology with a telephone to a data collection centre where results are tabulated and then forwarded to the doctor's office.
      • Omboni S.
      • Gazzola T.
      • Carabelli G.
      • Parati G.
      Clinical usefulness and cost effectiveness of home blood pressure telemonitoring: meta-analysis of randomized controlled studies.
      Telemonitoring of BP readings minimizes the human factor in home BP measurement by preventing selective reporting of measurements. However, home BP telemonitoring is expensive and its current use is mostly limited to health maintenance organizations or government operated health care plans.
      Home BP and manual BP measurements in routine clinical practice are both subject to human factors that limit the accuracy and reliability of the readings.
      • Myers M.G.
      Eliminating the human factor in office blood pressure measurement.
      The 2015 CHEP guidelines
      • Daskalopoulou S.S.
      • Rabi D.M.
      • Zarnke K.B.
      • et al.
      The 2015 Canadian Hypertension Education Program recommendations for blood pressure measurement, diagnosis, assessment of risk, prevention, and treatment of hypertension.
      recommend 24-hour ABPM as the best method for diagnosing hypertension. Not only is the use of ABPM supported by the strongest clinical outcome data,
      • O’Brien E.
      • Parati G.
      • Stergiou G.
      • et al.
      European Society of Hypertension position paper on ambulatory blood pressure monitoring.
      but this technique also involves the least involvement of humans in the assessment of BP status. Similarly, the CHEP guidelines recommend automated office BP measurement which also minimizes human factors
      • Myers M.G.
      Eliminating the human factor in office blood pressure measurement.
      that might often affect the accuracy of manual BP readings.
      Notwithstanding the concerns about reporting bias and the quality of home BP readings in clinical practice, as reported by Milot et al.,
      • Milot J.P.
      • Birnbaum L.
      • Larochelle P.
      • et al.
      Unreliability of home blood pressure measurement and the effect of a patient-oriented intervention.
      home BP is still important in the diagnosis and management of hypertension. There is considerable evidence from clinical outcome studies that show that home BP measurement is a better predictor of future cardiovascular events than manual office measurement.
      • Stergiou G.S.
      • Siontis K.C.
      • Ioannidis J.P.
      Home blood pressure as a cardiovascular outcome predictor.
      The CHEP guidelines recognize the value of home BP in the diagnosis of hypertension by recommending its use when 24-hour ABPM is not feasible. Improvements in the accuracy of home BP measurement and more reliable transmission of readings to health care providers would make home BP a more attractive alternative to ABPM in the out-of-office assessment of a patient's BP status.

      Disclosures

      The author is a consultant to Ideal Life Inc.

      References

        • Daskalopoulou S.S.
        • Rabi D.M.
        • Zarnke K.B.
        • et al.
        The 2015 Canadian Hypertension Education Program recommendations for blood pressure measurement, diagnosis, assessment of risk, prevention, and treatment of hypertension.
        Can J Cardiol. 2015; 31: 549-568
        • Stergiou G.S.
        • Siontis K.C.
        • Ioannidis J.P.
        Home blood pressure as a cardiovascular outcome predictor.
        Hypertension. 2010; 55: 1301-1303
        • Myers M.G.
        The great myth of office blood pressure measurement.
        J Hypertens. 2012; 30: 1894-1898
        • Milot J.P.
        • Birnbaum L.
        • Larochelle P.
        • et al.
        Unreliability of home blood pressure measurement and the effect of a patient-oriented intervention.
        Can J Cardiol. 2015; 31: 658-663
        • Parati G.
        • Stergiou G.S.
        • Asmar R.
        • et al.
        European Society of Hypertension guidelines for blood pressure monitoring at home: a summary report of the Second International Consensus Conference on Home Blood Pressure Monitoring.
        J Hypertens. 2008; 26: 1505-1526
        • Sedgwick P.
        The Hawthorne effect.
        BMJ. 2011; 344: d8262
        • Myers M.G.
        Self-measurement of blood pressure at home: the potential for reporting bias.
        Blood Press Monit. 1998; 3: S19-22
        • Mengden T.
        • Hernandez Medina R.M.
        • Beltran B.
        • et al.
        Reliability of reporting self-measurement of blood pressure values by hypertensive patients.
        Am J Hypertens. 1998; 11: 1413-1417
        • Myers M.G.
        • Stergiou G.S.
        Reporting bias: the Achilles heel of home blood pressure measurement.
        J Am Soc Hypertens. 2014; 8: 350-357
        • Omboni S.
        • Gazzola T.
        • Carabelli G.
        • Parati G.
        Clinical usefulness and cost effectiveness of home blood pressure telemonitoring: meta-analysis of randomized controlled studies.
        J Hypertens. 2013; 31: 455-468
        • Myers M.G.
        Eliminating the human factor in office blood pressure measurement.
        J Clin Hypertens. 2014; 16: 83-86
        • O’Brien E.
        • Parati G.
        • Stergiou G.
        • et al.
        European Society of Hypertension position paper on ambulatory blood pressure monitoring.
        J Hypertens. 2013; 31: 1731-1768

      Linked Article

      • The 2015 Canadian Hypertension Education Program Recommendations for Blood Pressure Measurement, Diagnosis, Assessment of Risk, Prevention, and Treatment of Hypertension
        Canadian Journal of CardiologyVol. 31Issue 5
        • Preview
          The Canadian Hypertension Education Program reviews the hypertension literature annually and provides detailed recommendations regarding hypertension diagnosis, assessment, prevention, and treatment. This report provides the updated evidence-based recommendations for 2015. This year, 4 new recommendations were added and 2 existing recommendations were modified. A revised algorithm for the diagnosis of hypertension is presented. Two major changes are proposed: (1) measurement using validated electronic (oscillometric) upper arm devices is preferred over auscultation for accurate office blood pressure measurement; (2) if the visit 1 mean blood pressure is increased but < 180/110 mm Hg, out-of-office blood pressure measurements using ambulatory blood pressure monitoring (preferably) or home blood pressure monitoring should be performed before visit 2 to rule out white coat hypertension, for which pharmacologic treatment is not recommended.
        • Full-Text
        • PDF
      • Unreliability of Home Blood Pressure Measurement and the Effect of a Patient-Oriented Intervention
        Canadian Journal of CardiologyVol. 31Issue 5
        • Preview
          Home blood pressure (BP) measurement (HBPM) is recommended for the diagnosis and follow-up of high BP. It is unclear how this aspect of BP monitoring has evolved over the years and whether interventions could influence patient adherence to HBPM guidelines.
        • Full-Text
        • PDF