title: Principles for modeling propensity scores in medical research: a systematic literature review.
abstract: OBJECTIVE
  To document which established criteria for logistic regression modeling researchers consider when using propensity scores in observational studies.
  
  
  METHODS
  We performed a systematic review searching Medline and Science Citation to identify observational studies published in 2001 that addressed clinical questions using propensity score methods to adjust for treatment assignment. We abstracted aspects of propensity score model development (e.g. variable selection criteria, continuous variables included in correct functional form, interaction inclusion criteria), model discrimination and goodness of fit for 47 studies meeting inclusion criteria.
  
  
  RESULTS
  We found few studies reporting on the propensity score model development or evaluation of model fit.
  
  
  CONCLUSIONS
  Reporting of aspects related to propensity score model development is limited and raises questions about the value of these principles in developing propensity scores from which unbiased treatment effects are estimated.
authors.affiliation: Department of Community Health, Brown Medical School, Providence, RI 02912, USA. Sherry_Weitzen@Brown.edu
authors.forename: Sherry
authors.initials: S
authors.lastname: Weitzen
authors.forename: Kate L
authors.initials: KL
authors.lastname: Lapane
authors.forename: Alicia Y
authors.initials: AY
authors.lastname: Toledano
authors.forename: Anne L
authors.initials: AL
authors.lastname: Hume
authors.forename: Vincent
authors.initials: V
authors.lastname: Mor
mesh_terms: D015982:Bias; D035843:Biomedical Research / Q000706:statistics & numerical data*; D016015:Logistic Models; D015233:Models, Statistical; D012107:Research Design / Q000592:standards