title: Revisiting issues, drawbacks and opportunities with observational studies in comparative effectiveness research.
abstract: BACKGROUND
  Despite their inherently pervasive limitations, data from observational studies are increasingly relied upon by health care decision makers to fill critical information gaps created by lack of evidence from randomized controlled trials.
  
  
  OBJECTIVE
  The aim and objective of this article was to revisit the major issues associated with observational studies from secondary data sources.
  
  
  METHODS
  The method of this article was canvass of the literature.
  
  
  RESULTS
  Sources of bias are highlighted and steps intended to minimize bias are summarized.
  
  
  CONCLUSIONS
  Efforts should be made to improve causal inference of treatment effects from observational studies found in secondary data sources. Extra care and caution should be exercised in the interpretation and reporting of results from these studies.
authors: Specialty Care Biostatistics, Pfizer Inc., New York, NY, USA.
authors: Demissie
authors: D
authors: Alemayehu
authors: Joseph C
authors: JC
authors: Cappelleri
mesh_terms: D015982:Bias; D015706:Bibliometrics; D002985:Clinical Protocols; D057186:Comparative Effectiveness Research / Q000379:methods* / Q000592:standards*; D003627:Data Interpretation, Statistical; D003657:Decision Making; D006801:Humans; D064887:Observational Studies as Topic / Q000592:standards*; D017410:Practice Guidelines as Topic; D015203:Reproducibility of Results