title: Adaptive designs for comparative effectiveness research trials.
abstract: BACKGROUND
  Medical and health policy decision makers require improved design and analysis methods for comparative effectiveness research (CER) trials. In CER trials, there may be limited information to guide initial design choices. In general settings, adaptive designs (ADs) have effectively overcome limits on initial information. However, CER trials have fundamental differences from standard clinical trials including population heterogeneity and a vaguer concept of a "minimum clinically meaningful difference".
  
  
  OBJECTIVE
  To explore the use of a particular form of ADs for comparing treatments within the CER trial context.
  
  
  METHODS
  We review the current state of clinical CER, identify areas of CER as particularly strong candidates for application of novel ADs, and illustrate potential usefulness of the designs and methods for two group comparisons.
  
  
  RESULTS
  ADs can stabilize power. The designs ensure adequate power for true effects are at least at clinically significant preplanned effect size, or when variability is larger than expected. The designs allow for sample size savings when the true effect is larger or when variability is smaller than planned.
  
  
  CONCLUSIONS
  ADs in CER have great potential to allow trials to successfully and efficiently make important comparisons.
authors: Department of Biostatistics, University of Florida, Gainesville, FL, USA.
authors: John A
authors: JA
authors: Kairalla
authors: Department of Biostatistics, University of Iowa, Iowa City, IA, USA.
authors: Christopher S
authors: CS
authors: Coffey
authors: Department of Biostatistics, University of Iowa, Iowa City, IA, USA.
authors: Mitchell A
authors: MA
authors: Thomann
authors: Department of Epidemiology, University of Florida, Gainesville, FL, USA; Geriatric Research Education and Clinical Center (GRECC), Malcom Randall Veterans Affairs Medical Center, Gainesville, FL, USA.
authors: Ronald I
authors: RI
authors: Shorr
authors: Department of Health Outcomes and Policy, University of Florida, Gainesville, FL, USA.
authors: Keith E
authors: KE
authors: Muller