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Prospective external validation of the Predicting Out-of-OFfice Blood Pressure (PROOF-BP) strategy for triaging ambulatory monitoring in the diagnosis and management of hypertension: observational cohort study

BMJ 2018; 361 doi: (Published 27 June 2018) Cite this as: BMJ 2018;361:k2478
  1. James P Sheppard, senior research fellow1,
  2. Una Martin, professor2,
  3. Paramjit Gill, professor3,
  4. Richard Stevens, associate professor1,
  5. FD Richard Hobbs, professor1,
  6. Jonathan Mant, professor4,
  7. Marshall Godwin, professor5,
  8. Janet Hanley, reader6,
  9. Brian McKinstry, professor7,
  10. Martin Myers, professor8,
  11. David Nunan, senior research fellow1,
  12. Richard J McManus, professor1
  13. on behalf of the PROOF-BP investigators
  1. 1Nuffield Department of Primary Care Health Sciences, University of Oxford, Radcliffe Primary Care, OX2 6GG Oxford, UK
  2. 2Institute of Clinical Sciences, University of Birmingham, Birmingham, UK
  3. 3Warwick Medical School, University of Warwick, Coventry, UK
  4. 4University of Cambridge, Cambridge, UK
  5. 5Memorial University of Newfoundland, St John’s, Canada
  6. 6Edinburgh Napier University, Edinburgh, UK
  7. 7University of Edinburgh, Edinburgh, UK
  8. 8University of Toronto, Toronto, Canada
  1. Correspondence to: JP Sheppard james.sheppard{at} (@jamessheppard48 on Twitter)
  • Accepted 7 May 2018


Objective To prospectively validate the Predicting Out-of-OFfice Blood Pressure (PROOF-BP) algorithm to triage patients with suspected high blood pressure for ambulatory blood pressure monitoring (ABPM) in routine clinical practice.

Design Prospective observational cohort study.

Setting 10 primary care practices and one hospital in the UK.

Participants 887 consecutive patients aged 18 years or more referred for ABPM in routine clinical practice. All underwent ABPM and had the PROOF-BP applied.

Main outcome measures The main outcome was the proportion of participants whose hypertensive status was correctly classified using the triaging strategy compared with the reference standard of daytime ABPM. Secondary outcomes were the sensitivity, specificity, and area under the receiver operator characteristic curve (AUROC) for detecting hypertension.

Results The mean age of participants was 52.8 (16.2) years. The triaging strategy correctly classified hypertensive status in 801 of the 887 participants (90%, 95% confidence interval 88% to 92%) and had a sensitivity of 97% (95% confidence interval 96% to 98%) and specificity of 76% (95% confidence interval 71% to 81%) for hypertension. The AUROC was 0.86 (95% confidence interval 0.84 to 0.89). Use of triaging, rather than uniform referral for ABPM in routine practice, would have resulted in 435 patients (49%, 46% to 52%) being referred for ABPM and the remainder managed on the basis of their clinic measurements. Of these, 69 (8%, 6% to 10%) would have received treatment deemed unnecessary had they received ABPM.

Conclusions In a population of patients referred for ABPM, this new triaging approach accurately classified hypertensive status for most, with half the utilisation of ABPM compared with usual care. This triaging strategy can therefore be recommended for diagnosis or management of hypertension in patients where ABPM is being considered, particularly in settings with limited resources.


  • Contributors: JS, UM, PG, and RJMcM had the original idea. JS managed the study, undertook the analysis, and wrote the first draft of the manuscript, with support from RS, UM, and RJMcM. All authors subsequently refined the manuscript and approved the final version. JS is the guarantor.

  • Funding: This work was funded by a Medical Research Council (MRC) strategic skills postdoctoral fellowship held by JS (MR/K022032/1). JS is now supported by a National Institute for Health Research (NIHR) professorship held by RJMcM and both receive additional support from the NIHR Oxford Collaboration for Leadership in Applied Health Research & Care. The views and opinions expressed are those of the authors and do not necessarily reflect those of the MRC, National Health Service, NIHR, or the Department of Health. Equipment used in the study was purchased commercially.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare: support from the MRC and NIHR for the submitted work; support from Omron, outside the submitted work; no financial relationships with any other 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: This study was approved by the National Research Ethics Service Committee South Central–Oxford A (reference 15/SC/0184), and site specific research and development approval acquired from the relevant NHS trusts.

  • Data sharing: Anonymised, patient level data are available from the corresponding author upon request, subject to submission of a suitable study protocol and analysis plan.

  • Transparency: The manuscript’s guarantor (JPS) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained.

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