title: Practical considerations for estimating clinical trial accrual periods: application to a multi-center effectiveness study.
abstract: BACKGROUND
  Adequate participant recruitment is vital to the conduct of a clinical trial. Projected recruitment rates are often over-estimated, and the time to recruit the target population (accrual period) is often under-estimated.
  
  
  METHODS
  This report illustrates three approaches to estimating the accrual period and applies the methods to a multi-center, randomized, placebo controlled trial undergoing development.
  
  
  RESULTS
  Incorporating known sources of accrual variation can yield a more justified estimate of the accrual period. Simulation studies can be incorporated into a clinical trial's planning phase to provide estimates for key accrual summaries including the mean and standard deviation of the accrual period.
  
  
  CONCLUSIONS
  The accrual period of a clinical trial should be carefully considered, and the allocation of sufficient time for participant recruitment is a fundamental aspect of planning a clinical trial.
authors.affiliation: Department of Biostatistics, Bioinformatics and Epidemiology, Medical University of South Carolina, Charleston, SC, USA. carterre@musc.edu
authors.forename: Rickey E
authors.initials: RE
authors.lastname: Carter
authors.forename: Susan C
authors.initials: SC
authors.lastname: Sonne
authors.forename: Kathleen T
authors.initials: KT
authors.lastname: Brady
mesh_terms: D006801:Humans; D015337:Multicenter Studies as Topic / Q000379:methods*; D018579:Patient Selection; D016012:Poisson Distribution; D016032:Randomized Controlled Trials as Topic / Q000379:methods* / Q000706:statistics & numerical data; D012107:Research Design; D013269:Stochastic Processes; D013997:Time Factors