title: A systematic review of the impact of volume of surgery and specialization in Norwood procedure.
abstract: BACKGROUND
  The volume-outcome relationship is supposed to be stronger in high risk, low volume procedures. The aim of this systematic review is to examine the available literature on the effects of hospital and surgeon volume, specialization and regionalization on the outcomes of the Norwood procedure.
  
  
  METHODS
  A systematic literature search was performed in Medline, Embase, and the Cochrane Library. On the basis of titles and abstracts, articles of comparative studies were obtained in full-text in case of potential relevance and assessed for eligibility according to predefined inclusion criteria. All relevant data on study design, patient characteristics, hospital volume, surgeon volume and other institutional characteristics, as well as results were extracted in standardized tables. Study selection, data extraction and critical appraisal were carried out independently by two reviewers.
  
  
  RESULTS
  We included 10 studies. All but one study had an observational design. The number of analyzed patients varied from 75 to 2555. Overall, the study quality was moderate with a huge number of items with an unclear risk of bias. All studies investigating hospital volume indicated a hospital volume-outcome relationship, most of them even having significant results. The results were very heterogeneous for surgeon volume.
  
  
  CONCLUSIONS
  The volume-outcome relationship in the Norwood procedure can be supported. However, the magnitude of the volume effect is difficult to assess.
authors.affiliation: Institute for Research in Operative Medicine, Witten/Herdecke University, Ostmerheimer Str, 200, Building 38, Cologne D- 51109, Germany. dawid.pieper@uni-wh.de.
authors.forename: Dawid
authors.initials: D
authors.lastname: Pieper
authors.forename: Tim
authors.initials: T
authors.lastname: Mathes
authors.forename: Boulos
authors.initials: B
authors.lastname: Asfour
mesh_terms: D017052:Hospital Mortality; D006761:Hospitals / Q000706:statistics & numerical data*; D061847:Hospitals, High-Volume / Q000706:statistics & numerical data; D061846:Hospitals, Low-Volume / Q000706:statistics & numerical data; D006780:Hospitals, Rural / Q000706:statistics & numerical data; D006784:Hospitals, Teaching / Q000706:statistics & numerical data; D006786:Hospitals, Urban / Q000706:statistics & numerical data; D006801:Humans; D058327:Norwood Procedures / Q000401:mortality*; D017063:Outcome Assessment, Health Care; D014481:United States
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