title: An assessment of the cost-effectiveness of magnetic resonance, including diffusion-weighted imaging, in patients with transient ischaemic attack and minor stroke: a systematic review, meta-analysis and economic evaluation.
abstract: BACKGROUND
  Patients with transient ischaemic attack (TIA) or minor stroke need rapid treatment of risk factors to prevent recurrent stroke. ABCD2 score or magnetic resonance diffusion-weighted brain imaging (MR DWI) may help assessment and treatment.
  
  
  OBJECTIVE
  Is MR with DWI cost-effective in stroke prevention compared with computed tomography (CT) brain scanning in all patients, in specific subgroups or as 'one-stop' brain-carotid imaging? What is the current UK availability of services for stroke prevention?
  
  
  METHODS
  Published literature; stroke registries, audit and randomised clinical trials; national databases; survey of UK clinical and imaging services for stroke; expert opinion.
  
  
  METHODS
  Systematic reviews and meta-analyses of published/unpublished data. Decision-analytic model of stroke prevention including on a 20-year time horizon including nine representative imaging scenarios.
  
  
  RESULTS
  The pooled recurrent stroke rate after TIA (53 studies, 30,558 patients) is 5.2% [95% confidence interval (CI) 3.9% to 5.9%] by 7 days, and 6.7% (5.2% to 8.7%) at 90 days. ABCD2 score does not identify patients with key stroke causes or identify mimics: 66% of specialist-diagnosed true TIAs and 35-41% of mimics had an ABCD2 score of ≥ 4; 20% of true TIAs with ABCD2 score of < 4 had key risk factors. MR DWI (45 studies, 9078 patients) showed an acute ischaemic lesion in 34.3% (95% CI 30.5% to 38.4%) of TIA, 69% of minor stroke patients, i.e. two-thirds of TIA patients are DWI negative. TIA mimics (16 studies, 14,542 patients) make up 40-45% of patients attending clinics. UK survey (45% response) showed most secondary prevention started prior to clinic, 85% of primary brain imaging was same-day CT; 51-54% of patients had MR, mostly additional to CT, on average 1 week later; 55% omitted blood-sensitive MR sequences. Compared with 'CT scan all patients' MR was more expensive and no more cost-effective, except for patients presenting at > 1 week after symptoms to diagnose haemorrhage; strategies that triaged patients with low ABCD2 scores for slow investigation or treated DWI-negative patients as non-TIA/minor stroke prevented fewer strokes and increased costs. 'One-stop' CT/MR angiographic-plus-brain imaging was not cost-effective.
  
  
  CONCLUSIONS
  Data on sensitivity/specificity of MR in TIA/minor stroke, stroke costs, prognosis of TIA mimics and accuracy of ABCD2 score by non-specialists are sparse or absent; all analysis had substantial heterogeneity.
  
  
  CONCLUSIONS
  Magnetic resonance with DWI is not cost-effective for secondary stroke prevention. MR was most helpful in patients presenting at > 1 week after symptoms if blood-sensitive sequences were used. ABCD2 score is unlikely to facilitate patient triage by non-stroke specialists. Rapid specialist assessment, CT brain scanning and identification of serious underlying stroke causes is the most cost-effective stroke prevention strategy.
  
  
  BACKGROUND
  The National Institute for Health Research Health Technology Assessment programme.
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Joanna
authors.initials: J
authors.lastname: Wardlaw
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Miriam
authors.initials: M
authors.lastname: Brazzelli
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Hector
authors.initials: H
authors.lastname: Miranda
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Francesca
authors.initials: F
authors.lastname: Chappell
authors.affiliation: Health Economics Research Unit, University of Aberdeen, Aberdeen, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: McNamee
authors.affiliation: Health Economics Research Unit, University of Aberdeen, Aberdeen, UK.
authors.forename: Graham
authors.initials: G
authors.lastname: Scotland
authors.affiliation: Health Economics Research Unit, University of Aberdeen, Aberdeen, UK.
authors.forename: Zahid
authors.initials: Z
authors.lastname: Quayyum
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Duncan
authors.initials: D
authors.lastname: Martin
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Shuler
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Sandercock
authors.affiliation: Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Dennis
mesh_terms: D000368:Aged; D003362:Cost-Benefit Analysis; D038524:Diffusion Magnetic Resonance Imaging / Q000191:economics*; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000175:diagnosis* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging / Q000191:economics / Q000379:methods; D020521:Stroke / Q000175:diagnosis* / Q000628:therapy; D014057:Tomography, X-Ray Computed / Q000191:economics