title: Adjusting outcome measurements for case-mix in a vascular surgical register--is it possible and desirable?
abstract: OBJECTIVE
  We analysed the variation in the outcome of infrainguinal bypass surgery between departments in a register for clinical audit to see if variation in case-mix influenced the results.
  
  
  METHODS
  The study was a retrospective analysis of 764 infrainguinal bypass operations performed from 1988 to 1990 at six Swedish surgical departments. Results were assessed at 30 days and at 1 year postoperatively.
  
  
  RESULTS
  There was a significant variation (p < 0.01) in mortality and amputation rates both at 30 days and at 1 year and in patency rate at 30 days. There were also differences in case-mix. Differences were found in indication, location of distal anastomosis and graft type. Regression analysis found that mortality was influenced by age, diabetes and heart disease and patency rate by location of the distal anastomosis and graft type. When 'hospital' was added as a variable in the regression analysis it was also found to be a significant indicator.
  
  
  CONCLUSIONS
  Location of the distal anastomosis was the main factor in adjusting patency for case-mix.
authors.affiliation: Department of Vascular Surgery, University Hospital, Linköping, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Elfström
authors.forename: T
authors.initials: T
authors.lastname: Troëng
authors.forename: A
authors.initials: A
authors.lastname: Stubberöd
mesh_terms: D000368:Aged; D000671:Amputation, Surgical / Q000706:statistics & numerical data; D001157:Arterial Occlusive Diseases / Q000401:mortality / Q000601:surgery*; D016009:Chi-Square Distribution; D003953:Diagnosis-Related Groups / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D016017:Odds Ratio; D012042:Registries; D012044:Regression Analysis; D012189:Retrospective Studies; D015996:Survival Rate; D013548:Sweden / Q000453:epidemiology; D016896:Treatment Outcome; D014654:Vascular Patency; D014656:Vascular Surgical Procedures / Q000706:statistics & numerical data*; D014680:Veins / Q000637:transplantation*