title: Optimizing stroke clinical trial design: estimating the proportion of eligible patients.
abstract: OBJECTIVE
  Clinical trial planning and site selection require an accurate estimate of the number of eligible patients at each site. In this study, we developed a tool to calculate the proportion of patients who would meet a specific trial's age, baseline severity, and time to treatment inclusion criteria.
  
  
  METHODS
  From a sample of 1322 consecutive patients with acute ischemic cerebrovascular syndromes, we developed regression curves relating the proportion of patients within each range of the 3 variables. We used half the patients to develop the model and the other half to validate it by comparing predicted vs actual proportions who met the criteria for 4 current stroke trials.
  
  
  RESULTS
  The predicted proportion of patients meeting inclusion criteria ranged from 6% to 28% among the different trials. The proportion of trial-eligible patients predicted from the first half of the data were within 0.4% to 1.4% of the actual proportion of eligible patients. This proportion increased logarithmically with National Institutes of Health Stroke Scale score and time from onset; lowering the baseline limits of the National Institutes of Health Stroke Scale score and extending the treatment window would have the greatest impact on the proportion of patients eligible for a stroke trial.
  
  
  CONCLUSIONS
  This model helps estimate the proportion of stroke patients eligible for a study based on different upper and lower limits for age, stroke severity, and time to treatment, and it may be a useful tool in clinical trial planning.
authors.affiliation: Section on Stroke Diagnostics and Therapeutics, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland 20892-1063, USA.
authors.forename: Alexis
authors.initials: A
authors.lastname: Taylor
authors.forename: Amanda
authors.initials: A
authors.lastname: Castle
authors.forename: José G
authors.initials: JG
authors.lastname: Merino
authors.forename: Amie
authors.initials: A
authors.lastname: Hsia
authors.forename: Chelsea S
authors.initials: CS
authors.lastname: Kidwell
authors.forename: Steven
authors.initials: S
authors.lastname: Warach
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000628:therapy*; D002986:Clinical Trials as Topic / Q000379:methods*; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D012107:Research Design; D012189:Retrospective Studies; D020521:Stroke / Q000628:therapy*; D016896:Treatment Outcome
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