title: Enrollment bias: frequency and impact on patient selection in endovascular stroke trials.
abstract: BACKGROUND
  Selection bias may have affected enrollment in first generation endovascular stroke trials. We investigate, evaluate, and quantify such bias for these trials at our institution.
  
  
  METHODS
  Demographic, clinical, imaging, and angiographic data were prospectively collected on a consecutive cohort of patients with acute ischemic stroke who were enrolled in formal trials of endovascular stroke therapy (EST) or received EST in clinical practice outside of a randomized trial for acute cerebral ischemia at a single tertiary referral center from September 2004 to December 2012.
  
  
  RESULTS
  Among patients considered appropriate for EST in practice, 47% were eligible for trials, with rates for individual trials ranging from 17% to 70%. Compared with trial ineligible patients treated with EST, trial eligible patients were younger (67 vs. 74 years; p<0.05), more often treated with intravenous tissue plasminogen activator (53% vs. 34%; p<0.01), and had shorter last known well to puncture times (328 vs. 367 min; p<0.05). Focusing on the largest trial with a non-interventional control arm, compared with trial eligible patients treated with EST outside the trial, enrolled patients presented later (274 vs. 163 min; p<0.001), had higher National Institutes of Health Stroke Scale scores (20 vs. 17; p<0.05), and larger strokes (diffusion weighted imaging volumes 49 vs. 18; p<0.001).
  
  
  CONCLUSIONS
  The majority of patients felt suitable for EST at our institution were excluded from recent trials. Formal entry criteria succeeded in selecting patients with better prognostic features, although many of these patients were treated outside of trials. Acknowledging and mitigating these biases will be crucial to ongoing investigations.
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA Division of Interventional Neuroradiology, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Sunil A
authors.initials: SA
authors.lastname: Sheth
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Saver
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA Department of Emergency Medicine, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Sidney
authors.initials: S
authors.lastname: Starkman
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA Department of Emergency Medicine, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Ileana D
authors.initials: ID
authors.lastname: Grunberg
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA Department of Emergency Medicine, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Judy
authors.initials: J
authors.lastname: Guzy
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Latisha K
authors.initials: LK
authors.lastname: Ali
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Doojin
authors.initials: D
authors.lastname: Kim
authors.affiliation: Division of Interventional Neuroradiology, University of California Los Angeles, Los Angeles, California, USA Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Nestor R
authors.initials: NR
authors.lastname: Gonzalez
authors.affiliation: Division of Interventional Neuroradiology, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Jahan
authors.affiliation: Division of Interventional Neuroradiology, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tateshima
authors.affiliation: Division of Interventional Neuroradiology, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Duckwiler
authors.affiliation: Department of Neurology, Comprehensive Stroke Center, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Liebeskind
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015982:Bias; D015331:Cohort Studies; D057510:Endovascular Procedures; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic / Q000379:methods*; D018579:Patient Selection; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D020521:Stroke / Q000453:epidemiology* / Q000601:surgery*; D013997:Time Factors
keywords: Angiography; Intervention; Political; Standards; Thrombectomy