Research

Conventional versus automated measurement of blood pressure in primary care patients with systolic hypertension: randomised parallel design controlled trial

BMJ 2011; 342 doi: 10.1136/bmj.d286 (Published 7 February 2011)
Cite this as: BMJ 2011;342:d286
  1. Martin G Myers, professor of medicine1,
  2. Marshall Godwin, professor of medicine2,
  3. Martin Dawes, professor of medicine3,
  4. Alexander Kiss, assistant professor4,
  5. Sheldon W Tobe, associate professor of medicine5,
  6. F Curry Grant, director6,
  7. Janusz Kaczorowski, professor of medicine7
  1. 1Schulich Heart Centre, Department of Medicine, University of Toronto, Toronto, ON, Canada
  2. 2Department of Family Medicine, Memorial University of Newfoundland, St John’s, NF, Canada
  3. 3Department of Family Medicine, McGill University, Montreal, QC, Canada
  4. 4Department of Research Design and Biostatistics, Sunnybrook Health Sciences Centre, Toronto
  5. 5Department of Medicine, University of Toronto
  6. 6Stroke Prevention Clinic, Quinte Health Care, Belleville, ON, Canada.
  7. 7Department of Family Practice, University of British Columbia, Vancouver, Canada
  1. Correspondence to: M Myers, Schulich Heart Centre, Division of Cardiology, Sunnybrook Health Sciences Centre, A-202, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5 martin.myers{at}sunnybrook.ca
  • Accepted 28 November 2010

Abstract

Objective To compare the quality and accuracy of manual office blood pressure and automated office blood pressure using the awake ambulatory blood pressure as a gold standard.

Design Multi-site cluster randomised controlled trial.

Setting Primary care practices in five cities in eastern Canada.

Participants 555 patients with systolic hypertension and no serious comorbidities under the care of 88 primary care physicians in 67 practices in the community.

Interventions Practices were randomly allocated to either ongoing use of manual office blood pressure (control group) or automated office blood pressure (intervention group) using the BpTRU device. The last routine manual office blood pressure (mm Hg) was obtained from each patient’s medical record before enrolment. Office blood pressure readings were compared before and after enrolment in the intervention and control groups; all readings were also compared with the awake ambulatory blood pressure.

Main outcome measure Difference in systolic blood pressure between awake ambulatory blood pressure minus automated office blood pressure and awake ambulatory blood pressure minus manual office blood pressure.

Results Cluster randomisation allocated 31 practices (252 patients) to manual office blood pressure and 36 practices (303 patients) to automated office blood pressure measurement. The most recent routine manual office blood pressure (149.5 (SD 10.8)/81.4 (8.3)) was higher than automated office blood pressure (135.6 (17.3)/77.7 (10.9)) (P<0.001). In the control group, routine manual office blood pressure before enrolment (149.9 (10.7)/81.8 (8.5)) was reduced to 141.4 (14.6)/80.2 (9.5) after enrolment (P<0.001/P=0.01), but the reduction in the intervention group from manual office to automated office blood pressure was significantly greater (P<0.001/P=0.02). On the first study visit after enrolment, the estimated mean difference for the intervention group between the awake ambulatory systolic/diastolic blood pressure and automated office blood pressure (−2.3 (95% confidence interval −0.31 to −4.3)/−3.3 (−2.7 to −4.4)) was less (P=0.006/P=0.26) than the difference in the control group between the awake ambulatory blood pressure and the manual office blood pressure (−6.5 (−4.3 to −8.6)/−4.3 (−2.9 to −5.8)). Systolic/diastolic automated office blood pressure showed a stronger (P<0.001) within group correlation (r=0.34/r=0.56) with awake ambulatory blood pressure after enrolment compared with manual office blood pressure versus awake ambulatory blood pressure before enrolment (r=0.10/r= 0.40); the mean difference in r was 0.24 (0.12 to 0.36)/0.16 (0.07 to 0.25)). The between group correlation comparing diastolic automated office blood pressure and awake ambulatory blood pressure (r=0.56) was stronger (P<0.001) than that for manual office blood pressure versus awake ambulatory blood pressure (r=0.30); the mean difference in r was 0.26 (0.09 to 0.41). Digit preference with readings ending in zero was substantially reduced by use of automated office blood pressure.

Conclusion In compliant, otherwise healthy, primary care patients with systolic hypertension, introduction of automated office blood pressure into routine primary care significantly reduced the white coat response compared with the ongoing use of manual office blood pressure measurement. The quality and accuracy of automated office blood pressure in relation to the awake ambulatory blood pressure was also significantly better when compared with manual office blood pressure.

Trial registration Clinical trials NCT 00214053.

Footnotes

  • We thank the primary care physicians and research assistants who participated in this study, which would not have been possible without their cooperation and strong commitment to the project (see web appendix for participating physicians).

  • Contributors: MGM is the principal investigator and was involved in all aspects from the development of the protocol to drafting the final manuscript and its revisions. MG participated in the design of the study, supervised the sites in St John’s and Corner Brook, Newfoundland, and reviewed the manuscript and its revisions. MD was involved in the design of the study, supervised the sites in Montreal, and reviewed the manuscript and its revisions. AK was the statistician for the study, was involved in the initial sample size estimates and subsequent data analysis on completion of the trial, and advised on how to incorporate the data analysis into the final manuscript. SWT and JK contributed to the design of the study, review of the data, and preparation of the final manuscript. FCG supervised the sites in Belleville, Ontario, assisted with recruitment of patients, and reviewed the manuscript and its revisions. MGM is the guarantor.

  • Funding: The study was supported by Grant ESA5745 from the Heart and Stroke Foundation of Ontario.

  • Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: The study was approved by the Research Ethics Board of Sunnybrook Health Sciences Centre, Human Investigation Committee of Memorial University of Newfoundland, Institutional Review Board of McGill University Faculty of Medicine, St Mary’s Hospital Center’s Research Review Office, and Comité D’éthique De La Recherche, Centre de Santé et de services sociaux de la Montagne.

  • Data sharing: No additional data available.

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.

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