title: Adjusted Hospital Outcomes of Abdominal Aortic Aneurysm Surgery Reported in the Dutch Surgical Aneurysm Audit.
abstract: OBJECTIVE
  The Dutch Surgical Aneurysm Audit (DSAA) is mandatory for all patients with primary abdominal aortic aneurysms (AAAs) in the Netherlands. The aims are to present the observed outcomes of AAA surgery against the predicted outcomes by means of V-POSSUM (Vascular-Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity). Adjusted mortality was calculated by the original and re-estimated V(physiology)-POSSUM for hospital comparisons.
  
  
  METHODS
  All patients operated on from January 2013 to December 2014 were included for analysis. Calibration and discrimination of V-POSSUM and V(p)-POSSUM was analysed. Mortality was benchmarked by means of the original V(p)-POSSUM formula and risk-adjusted by the re-estimated V(p)-POSSUM on the DSAA.
  
  
  RESULTS
  In total, 5898 patients were included for analysis: 4579 with elective AAA (EAAA) and 1319 with acute abdominal aortic aneurysm (AAAA), acute symptomatic (SAAA; n = 371) or ruptured (RAAA; n = 948). The percentage of endovascular aneurysm repair (EVAR) varied between hospitals but showed no relation to hospital volume (EAAA: p = .12; AAAA: p = .07). EAAA, SAAA, and RAAA mortality was, respectively, 1.9%, 7.5%, and 28.7%. Elective mortality was 0.9% after EVAR and 5.0% after open surgical repair versus 15.6% and 27.4%, respectively, after AAAA. V-POSSUM overestimated mortality in most EAAA risk groups (p < .01). The discriminative ability of V-POSSUM in EAAA was moderate (C-statistic: .719) and poor for V(p)-POSSUM (C-statistic: .665). V-POSSUM in AAAA repair overestimated in high risk groups, and underestimated in low risk groups (p < .01). The discriminative ability in AAAA of V-POSSUM was moderate (.713) and of V(p)-POSSUM poor (.688). Risk adjustment by the re-estimated V(p)-POSSUM did not have any effect on hospital variation in EAAA but did in AAAA.
  
  
  CONCLUSIONS
  Mortality in the DSAA was in line with the literature but is not discriminative for hospital comparisons in EAAA. Adjusting for V(p)-POSSUM, revealed no association between hospital volume and treatment or outcome. Risk adjustment for case mix by V(p)-POSSUM in patients with AAAA has been shown to be important.
authors.affiliation: Department of Vascular Surgery, Leiden University Medical Centre, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands. Electronic address: n.lijftogt@gmail.com.
authors.forename: N
authors.initials: N
authors.lastname: Lijftogt
authors.affiliation: Department of Surgery, OLVG, Oosterpark 9, 1091 AC, Amsterdam, The Netherlands.
authors.forename: A C
authors.initials: AC
authors.lastname: Vahl
authors.affiliation: Department of Vascular Surgery, Leiden University Medical Centre, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.
authors.forename: E D
authors.initials: ED
authors.lastname: Wilschut
authors.affiliation: Department of Vascular Surgery, Deventer Hospital, Nico Bolkesteinlaan 75, 7416 SE, Deventer, The Netherlands.
authors.forename: B H P
authors.initials: BHP
authors.lastname: Elsman
authors.affiliation: Department of Medical Statistics, Leiden University, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Amodio
authors.affiliation: Department of Medical Statistics, Leiden University, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands.
authors.forename: E W
authors.initials: EW
authors.lastname: van Zwet
authors.affiliation: Department of Surgery, OLVG, Oosterpark 9, 1091 AC, Amsterdam, The Netherlands.
authors.forename: V J
authors.initials: VJ
authors.lastname: Leijdekkers
authors.affiliation: Department of Surgery, Dutch Cancer Institute - Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands; Scientific Bureau, Dutch Institute for Clinical Auditing, Rijnsburgerweg 10, 2333 AA, Leiden, The Netherlands.
authors.forename: M W J M
authors.initials: MWJM
authors.lastname: Wouters
authors.affiliation: Department of Vascular Surgery, Leiden University Medical Centre, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.
authors.forename: J F
authors.initials: JF
authors.lastname: Hamming
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging / Q000401:mortality / Q000601:surgery*; D001019:Aortic Rupture / Q000000981:diagnostic imaging / Q000401:mortality / Q000601:surgery*; D019985:Benchmarking; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000401:mortality; D017558:Elective Surgical Procedures; D057510:Endovascular Procedures / Q000009:adverse effects / Q000401:mortality; D005260:Female; D017052:Hospital Mortality; D006761:Hospitals; D006801:Humans; D008297:Male; D008485:Medical Audit; D009426:Netherlands; D019984:Quality Indicators, Health Care; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome
keywords: Abdominal aortic aneurysm; Case-mix adjustment; Clinical audit; Quality of health care