title: Procedure Volume and the Association with Short-term Mortality Following Abdominal Aortic Aneurysm Repair in European Populations: A Systematic Review.
abstract: OBJECTIVE
  To evaluate the relationship between the volume of abdominal aortic aneurysm (AAA) procedures undertaken and the primary outcome of mortality in Europe. Previous systematic reviews of this relationship are outdated and are overwhelmingly based on US data.
  
  
  METHODS
  Comprehensive searching within MEDLINE and other bibliographic databases supplemented by citation searching and hand-searching of journals was undertaken to identify studies that reported the effect of hospital or clinician volume on any reported outcomes in adult, European populations, undergoing AAA repair and published in the last 10 years.
  
  
  METHODS
  Two reviewers conducted study selection with independent, duplicate data extraction and quality assessment. A planned meta-analysis was not conducted because of the high risk of bias, the likelihood of individual study subjects being included in more than one study and diversity in the clinical populations studied and methods used.
  
  
  RESULTS
  Sixteen studies (n = 237,074 participants) from the UK (n = 11 studies), Germany (n = 3 studies), Norway (n = 1 study), and one from the UK and Sweden were included. Data in the included studies came from administrative databases and clinical registries incorporating a variety of clinical and procedural groups; the study quality was limited by the use of observational study designs. Overall, the evidence favoured the existence of an inverse volume outcome relationship between hospital volume and mortality. Insufficient evidence was available to reach conclusions on the relationship between clinician volume and outcome and between hospital or clinician volume and secondary outcomes including complications and length of hospital stay.
  
  
  CONCLUSIONS
  The evidence from this review suggests a relationship between the hospital volume of AAA procedures conducted and short-term mortality; however, as volume typically represents a complex amalgamation of factors further research will be useful to identify the core characteristics of volume that influence improved outcomes.
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK; Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK. Electronic address: p.phillips@sheffield.ac.uk.
authors.forename: P
authors.initials: P
authors.lastname: Phillips
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: E
authors.initials: E
authors.lastname: Poku
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: M
authors.initials: M
authors.lastname: Essat
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: H B
authors.initials: HB
authors.lastname: Woods
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Goka
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: E C
authors.initials: EC
authors.lastname: Kaltenthaler
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: S
authors.initials: S
authors.lastname: Walters
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: P
authors.initials: P
authors.lastname: Shackley
authors.affiliation: School of Health & Related Research (ScHARR), The University of Sheffield, Sheffield, UK.
authors.forename: J
authors.initials: J
authors.lastname: Michaels
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000401:mortality* / Q000601:surgery*; D001019:Aortic Rupture / Q000401:mortality / Q000601:surgery; D004630:Emergencies; D005060:Europe; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D007902:Length of Stay; D011183:Postoperative Complications / Q000401:mortality*; D014656:Vascular Surgical Procedures / Q000009:adverse effects / Q000706:statistics & numerical data*
keywords: Abdominal aortic aneurysm; High volume; Hospitals; Low volume; Operative; Review; Surgical procedures; Workload