title: Temporal trends and differences in mortality at trauma centres across Ontario from 2005 to 2011: a retrospective cohort study.
abstract: BACKGROUND
  Care in a trauma centre is associated with significant reductions in mortality after severe injury. However, emerging evidence suggests that outcomes across similarly accredited trauma centres are not equivalent, even after adjusting for case-mix. The primary objective of this analysis was to evaluate secular trends in overall mortality at trauma centres. Secondarily, we explored trauma centre-specific mortality to determine the extent of variation between centres.
  
  
  METHODS
  Data on 26 421 adults (≥□18 yr) admitted to a trauma centre between 2005 and 2011 were derived from the Ontario Trauma Registry. We used generalized estimating equations to calculate in-hospital mortality over time and hierarchical models to estimate trauma-centre-specific mortality. To quantify variability between centres, we calculated median odds ratios. Adjusted odds of death were calculated for each trauma centre to identify those with higher than expected, average and lower than expected mortality.
  
  
  RESULTS
  Overall mortality at trauma centres decreased from 13.2% in 2005 to 11.2% in 2009. After adjusting for case mix, the odds of death decreased by approximately 3% a year (95% confidence interval 0%-5%). Trauma centre-specific mortality ranged from 11.4% to 13.1%. After adjusting for case mix, differences in trauma centre-specific mortality were observed (median odds ratio = 1.25), suggesting that the odds of dying could be 1.25-fold greater if the same patient was admitted to 1 randomly selected trauma centre as opposed to another. Differences were most pronounced for patients with isolated head injuries and among older patients as evidenced by higher median odds ratios and the number of outliers.
  
  
  CONCLUSIONS
  We observed a significant improvement over time in the mortality of severely injured patients cared for at Ontario's trauma centres. However, considerable differences in trauma centre-specific mortality were observed. Differences were most pronounced among older injured patients and those with isolated traumatic brain injury. System-wide performance improvement initiatives should target these subgroups.
authors.affiliation: Department of Surgery and Division of General Surgery, University of Toronto, Toronto, Ont. ; Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ont.
authors.forename: David
authors.initials: D
authors.lastname: Gomez
authors.affiliation: Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ont. ; Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ont.
authors.forename: Aziz S
authors.initials: AS
authors.lastname: Alali
authors.affiliation: Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ont. ; Interdepartmental Division of Critical Care, University of Toronto, Toronto, Ont.
authors.forename: Barbara
authors.initials: B
authors.lastname: Haas
authors.affiliation: Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ont.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: Department of Surgery and Division of General Surgery, University of Toronto, Toronto, Ont. ; Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ont.
authors.forename: Homer
authors.initials: H
authors.lastname: Tien
authors.affiliation: Department of Surgery and Division of General Surgery, University of Toronto, Toronto, Ont. ; Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ont.
authors.forename: Avery B
authors.initials: AB
authors.lastname: Nathens