title: Quasi-experimental designs in practice-based research settings: design and implementation considerations.
abstract: BACKGROUND
  Although randomized controlled trials are often a gold standard for determining intervention effects, in the area of practice-based research (PBR), there are many situations in which individual randomization is not possible. Alternative approaches to evaluating interventions have received increased attention, particularly those that can retain elements of randomization such that they can be considered "controlled" trials.
  
  
  METHODS
  Methodological design elements and practical implementation considerations for two quasi-experimental design approaches that have considerable promise in PBR settings--the stepped-wedge design, and a variant of this design, a wait-list cross-over design, are presented along with a case study from a recent PBR intervention for patients with diabetes.
  
  
  RESULTS
  PBR-relevant design features include: creation of a cohort over time that collects control data but allows all participants (clusters or patients) to receive the intervention; staggered introduction of clusters; multiple data collection points; and one-way cross-over into the intervention arm. Practical considerations include: randomization versus stratification, training run in phases; and extended time period for overall study completion.
  
  
  CONCLUSIONS
  Several design features of practice based research studies can be adapted to local circumstances yet retain elements to improve methodological rigor. Studies that utilize these methods, such as the stepped-wedge design and the wait-list cross-over design, can increase the evidence base for controlled studies conducted within the complex environment of PBR.
authors: Department of Epidemiology and Biostatistics, Division of General Internal Medicine, University of California San Francisco, San Francisco General Hospital Center for Vulnerable Populations, San Francisco, CA 94110, USA. handleym@medsfgh.ucsf.edu
authors: Margaret A
authors: MA
authors: Handley
authors: Dean
authors: D
authors: Schillinger
authors: Stephen
authors: S
authors: Shiboski
mesh_terms: D016000:Cluster Analysis; D055812:Community-Based Participatory Research / Q000458:organization & administration*; D015986:Confounding Factors, Epidemiologic; D003920:Diabetes Mellitus / Q000628:therapy; D005069:Evaluation Studies as Topic; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012648:Self Care; D014850:Waiting Lists