C: Immediate CT scanning in acute stroke improves outcomes for patients and is very cost effective, whereas arteriography and MR scanning are not cost-effective in secondary prevention
Submitting InstitutionUniversity of Edinburgh
Unit of AssessmentPsychology, Psychiatry and Neuroscience
Summary Impact TypeHealth
Research Subject Area(s)
Medical and Health Sciences: Neurosciences
Summary of the impact
Impact: Health and welfare; Wardlaw's work on diagnostic imaging
in stroke prevention and treatment has effected changes to clinical
guidelines worldwide, prevented thousands of strokes and decreased
Significance: In the UK, changes in stroke treatment consequent
upon effective imaging result in 6000 more quality-adjusted life-years and
save ~£300M per year. Improved stroke prevention averts 1760 strokes and
saves the NHS £30M per year.
Beneficiaries: Stroke patients, the NHS and healthcare providers
in other countries
Attribution: The research took place entirely at UoE.
Reach: UK, Europe, N. America, Australasia.
Professor Joanna Wardlaw (Professor of Applied Neuroimaging, UoE,
1994-present) undertook ground-breaking studies to demonstrate that
immediate computerised tomography (CT) scanning in acute stroke was the
most cost-effective imaging strategy.
Attitudes to stroke were generally nihilistic in the late 1990s, with
poor access to imaging, often with long delays to diagnosis and in
initiating treatment. Wardlaw and her group determined how best to use
imaging in acute stroke diagnosis and prevention in three consecutive
reports; the first report in 2004 on cost-effective imaging in acute
stroke led to Wardlaw being commissioned, in open competition, to
undertake two further health economic impact assessments: in 2005-2006 on
cost-effective carotid imaging in stroke prevention and in 2010-2012 on
cost-effective brain imaging in stroke prevention.
2.1. Acute stroke imaging diagnosis: Between 1998 and 2004,
Wardlaw's group performed new primary studies and meta-analysed data on
the accuracy of CT and magnetic resonance (MR) imaging; examined the
effects of antithrombotic treatment given to patients with haemorrhagic
stroke; calculated the costs of stroke care and of imaging; measured the
effects of time-to-imaging after stroke on its accuracy; and devised
health utility states for different stroke outcomes. Wardlaw's group built
a health economics decision-tree model of stroke care and diagnosis, and
performed Markov analysis to determine the effect of common imaging
strategies on death and dependency after stroke and the cost-effectiveness
of different approaches. The most cost-effective imaging strategy was to
CT scan all patients admitted with acute stroke immediately [3.1-3.3].
2.2 Carotid imaging in stroke prevention: In secondary stroke
prevention, carotid stenosis is an important treatable risk factor for
stroke, but requires carotid imaging to diagnose the stenosis. Trials
(also led by UoE) in the 1990s used intra-arterial angiography to diagnose
carotid stenosis but this is time-consuming, carries significant risk of
causing stroke and was only available in specialist centres. Between 20
and 30 patients present to stroke prevention services with suspected
transient ischaemic attack (TIA) or minor stroke every week. Rapid access
to accurate imaging is essential for rapid diagnosis and treatment.
Wardlaw's group undertook a second health economics analysis between 2005
and 2007, meta-analysing existing data and acquiring new data on the
accuracy of non-invasive carotid imaging, gathering data on the costs of
imaging, treatments and on the population risks of stroke. They
constructed a time-series model of stroke prevention clinics, tested 18
different imaging strategies, and determined that intra-arterial
angiography should be abandoned as it was less effective than rapid
non-invasive imaging [3.4, 3.5].
2.3 MR brain imaging in stroke prevention: In 2010-2012, Wardlaw's
group undertook a third analysis to determine if MR brain imaging (which
is very sensitive to acute ischaemia) should be more widely used in stroke
prevention. Following detailed analyses of all available literature and
primary data, deterministic and probabilistic modelling, Wardlaw's group
demonstrated that MR diffusion-weighted imaging was too insensitive and
heterogeneous to differentiate stroke from TIA reliably, or to
differentiate TIA from mimics, and was highly unlikely to be
cost-effective in stroke prevention. Moreover, in some circumstances, a
reliance on MR could lead to fewer strokes being prevented [3.6].
References to the research
3.2 Wardlaw J, Seymour J, Cairns J,... Keir S, Dennis M, Sandercock P.
Immediate computed tomography scanning of acute stroke is cost effective
and improves quality of life. Stroke. 2004;35:2477-83. DOI:
3.3 Wardlaw J, Keir S, Bastin M, ... Armitage P, Rana A. Is diffusion
imaging appearance an independent predictor of outcome after ischemic
stroke? Neurology. 2002;59:1381-7. DOI:
3.4 Wardlaw J, Chappell F, Best J, ... Wartolowska K, Berry E, on behalf
of the NHS R & D Health Technology Assessment Carotid Stenosis Imaging
Group. Non-invasive imaging compared with intra-arterial angiography in
the diagnosis of symptomatic carotid stenosis: a meta-analysis. Lancet.
2006;367:1503-12. DOI: 10.1016/S0140-6736(06)68650-9.
3.5 Wardlaw J, Stevenson M, Chappell F, et al. Carotid artery imaging for
secondary stroke prevention: both imaging modality and rapid access to
imaging are important. Stroke. 2009;40:3511-7. DOI:
3.6 Wardlaw J, Brazelli M, Chappell F, et al. An assessment of the cost
effectiveness of magnetic resonance including diffusion-weighted imaging
in patients with transient ischaemic attack and minor stroke. Health
Technology Assessment. 2014, in press. [Will appear on www.journalslibrary.nihr.ac.uk
as a future publication in Oct/Nov 2013].
Details of the impact
Immediately following its publication in scientific journals, Wardlaw and
colleagues' work was highlighted in many secondary commentaries by highly
respected organisations that disseminate medical practice information; for
example, the American College of Physicians Journal Club publications and,
in the UK, the Database of Reviews of Effectiveness. The work was also
included in a best-selling international textbook on stroke management
Impact on public policy
The findings were cited by and led to changes to the guidelines on stroke
management in the UK and internationally. The National Institute for
Health and Care Excellence guidelines [5.2], European [5.3], Canadian
[5.4], Australasian [5.5] and the American Heart Association [5.6]
guidelines were changed in 2008 or subsequently. Wardlaw's recent survey
of UK practice [3.6] revealed that intra-arterial angiography has been
replaced rapidly and completely by non-invasive imaging. Data from 2012
(see below) clearly indicate that, as a result of Wardlaw's research and
these guidelines, a change in practice has occurred.
Wardlaw, with Chappell (CSO Health Services Research Fellow, UoE,
2002-present), Brazelli (CSO Health Services Research Fellows, UoE,
2010-2012) and Sandercock (UoE 1987-present; Professor of Medical
Neurology; Head of Cochrane Stroke Group) were foundation members of the
Cochrane Collaboration Diagnostic Tests Working Group, which is now
publishing key systematic reviews of the accuracy of diagnostic tests
[5.7], and important improvements in methodology. These increasingly
underpin evidence on which tests should be used in clinical practice,
particularly in the era of stratified medicine.
Impact on practitioners and services
A survey of UK stroke services by Wardlaw, published in 2008, showed that
fewer patients were waiting more than 24 hours for CT brain imaging
compared with a survey in 2000-2001 [5.8]. Wardlaw's Health Technology
Assessment panel-commissioned survey of all stroke prevention services in
the UK in 2012 [3.6] showed that no centres were using intra-arterial
angiography, and 90%+ were using ultrasound, most on the day of referral,
and had immediate access to CT brain imaging for stroke.
Impact on health and the economy
Performing immediate brain imaging in all patients with suspected acute
stroke, compared with the less-effective strategies, for the 120,000
patients who have a stroke each year in the UK is calculated to have
resulted in 6,000 more quality-adjusted life-years, and reduced the cost
of stroke by between £156M and £312M per year in NHS costs.
Rapid non-invasive carotid imaging in patients with TIA, compared with
the slow and more invasive carotid imaging methods, is calculated to have
prevented about 1760 strokes per year in the UK and saved the NHS around
£30M per year [3.5, 3.6].
Sources to corroborate the impact
5.1 Warlow C, van Gijn J, Dennis M, Wardlaw J,...Sandercock P, et al.
Stroke: Practical Management, Third Edition. Blackwell Scientific Ltd,
Oxford, 2008. ISBN 978-1-4051-2766-0. [Available on request.
Corroborates inclusion of the work in a best-selling textbook.]
5.2 UK STROKE. National clinical guideline for diagnosis and initial
management of acute stroke and transient ischaemic attack (TIA). NICE.
5.3 European Stroke Organization (ESO) Executive. Guidelines for
Management of Ischaemic Stroke and Transient Ischaemic Attack 2008.
Cerebrovasc Dis. 2008;25:457-507.
5.4 Canadian Best Practice Recommendations for Stroke Care (May 2013
5.5 The Australian National Stroke Foundation. Clinical Guidelines for
Stroke Management 2010.
5.6 Latchaw R, Alberts M, Lev M, et al. Recommendations for imaging of
acute ischemic stroke: a scientific statement from the American Heart
Association. Stroke. 2009;40:3646-78. DOI: 10.1161/STROKEAHA.108.192616. [American
Heart Association guidelines.]
5.7 Brazzelli M, Sandercock P,...Wardlaw J, Deeks J. Magnetic resonance
imaging versus computed tomography for detection of acute vascular lesions
in patients presenting with stroke symptoms. Cochrane Database
Sys Rev. 2008;4:CD007424. DOI:
10.1002/14651858.CD007424. [Systematic review of diagnostic test
5.8 Kane I, Whiteley W, Sandercock P, Wardlaw J. Availability of CT and
MR for assessing patients with acute stroke. Cerebrovasc Dis.
2008;25:375-7. DOI: 10.1159/000120688. [Corroborates change in