Hypertension: improving routine diagnosis in primary care

By Jesse K. Alwin, U.S. Marine Corps [Public domain], via Wikimedia Commons 

Lead investigators: Professor Richard McManus, Professor Richard Hobbs, Dr Pelham Barton, Dr James Hodgkinson and Dr Boliang Guo

Introduction

High blood pressure (hypertension) is the major cause of stroke and other cardiovascular disease, is the commonest chronic disorder seen in primary care and is one of the most important preventable causes of morbidity and mortality in developed and developing countries. In the UK it affects half the population over 60 and costs the NHS £1Bn per year in drugs alone, with around 1:8 receiving antihypertensive treatment. The prevalence of hypertension and requirement for effective treatment continues to rise as the demographics shift towards an older, more sedentary and obese population.

In 2009, a group from Primary Care led by Professors Richard McManus (up to 31 August 2011); Richard Hobbs (up to 30 April 2011); Drs Pelham Barton; James Hodgkinson and Boliang Guo and working with others in the University of Birmingham (Professor Jon Deeks and Dr Una Martin) and in the University of Oxford (Mant, Heneghan, Roberts) conducted a systematic review of the worldwide literature and a meta-analysis using hierarchical summary receiver-operating characteristic models. Funded by an NIHR Programme Grant for Applied Research, this research, which forms part of the Birmingham/ Oxford Universities Collaborative BP Monitoring Programme Group, has provided robust evidence of the superiority of ambulatory (ABPM) over clinic (CBPM) and home (HBPM) blood pressure monitoring in diagnosing hypertension.

Research objectives

Hypertension is currently diagnosed in primary care and in hospital clinics using the traditional technique of measurement by a GP or nurse with either a mercury sphygmomanometer and stethoscope or with an automated device. In terms of patient outcomes, these methods compare poorly with ABPM where a cuff connected to a portable monitor is worn continuously by the patient for a period of 24 hours. However, no previous study had attempted to bring together and synthesise the literature on the accuracy of diagnosis of hypertension using different methods of measurement.

The objective of the systematic review was to determine the relative accuracy of clinic measurements and home blood pressure monitoring compared with ambulatory blood pressure monitoring as a reference standard for the diagnosis of hypertension.

Research output

The research identified:

  • Compared with ABPM, neither CBPM nor HBPM have sufficient sensitivity or specificity to be recommended as a single diagnostic test.
  • If ABPM is taken as the reference standard, then treatment decisions based on CBPM or HBPM alone may result in substantial over-diagnosis (and subsequent over-medication and unnecessary cost).
  • For example, if the prevalence of hypertension in a screened population was 30%, there would only be a 56% chance that the clinic measurement would be correct compared with using the ABPM methods.
  • These results suggest that ambulatory monitoring prior to commencement of life-long drug treatment would lead to more appropriate targeting of treatment, particularly around the diagnostic threshold.
  • In conjunction with health economists at the University of Birmingham (Dr Sue Jowett and Dr Pelham Barton) and the National Clinical Guideline Centre (Lovibond, Wonderling) ambulatory monitoring was identified as the most cost effective strategy for the diagnosis of hypertension for men and women of all ages, and resulted in more quality-adjusted life years (QALYs) for male and female groups aged over 50. These findings were published in the Lancet in 2011 and received media coverage including television (ITV central), print newspapers (Daily Mail, Daily Express) and online (BBC).

Research impact

The University of Birmingham primary care-led study has provided definitive evidence of the superiority of ambulatory blood pressure measurement (ABPM) over clinic and home blood pressure monitoring as a means of diagnosing hypertension. The associated cost-effectiveness study showed that this approach will save the NHS over £10.5M per year. As a result of this research, NICE guidelines have been amended and ABPM has become the reference standard. The research has also influenced public and policy debate in the UK and internationally.

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