title: Ottawa Hospital Patient Safety Study: incidence and timing of adverse events in patients admitted to a Canadian teaching hospital.
abstract: BACKGROUND
  Adverse events are poor patient outcomes that are due to medical care. Studies of hospital patients have demonstrated that adverse events are common, but few data describe the timing of them in relation to hospital admission. We evaluated characteristics of adverse events affecting patients admitted to a Canadian teaching hospital, paying particular attention to timing.
  
  
  METHODS
  We randomly selected 502 adults admitted to the Ottawa Hospital for acute care of nonpsychiatric illnesses over a 1-year period. Charts were reviewed in 2 stages. If an adverse event was judged to have occurred, a physician determined whether it occurred before or during the index hospitalization. The reviewer also rated the preventability, severity and type of each adverse event.
  
  
  RESULTS
  Of the 64 patients with an adverse event (incidence 12.7%, 95% confidence interval [CI] 10.1%-16.0%), 24 had a preventable event (4.8%, 95% CI 3.2%-7.0%), and 3 (0.6%, 95% CI 0.2%-1.7%) died because of an adverse event. Most adverse events were due to drug treatment, operative complications or nosocomial infections. Of the 64 patients, 39 (61%, 95% CI 49%-72%) experienced the adverse event before the index hospitalization.
  
  
  CONCLUSIONS
  Adverse events were common in this study. However, only one-third were deemed avoidable, and most occurred before the hospitalization. Interventions to improve safety must address ambulatory care as well as hospital-based care.
authors.affiliation: Ottawa Health Research Institute, Ottawa, Ont. aforster@ohri.ca
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Forster
authors.forename: Tim R
authors.initials: TR
authors.lastname: Asmis
authors.forename: Heather D
authors.initials: HD
authors.lastname: Clark
authors.forename: Ghiath
authors.initials: G
authors.lastname: Al Saied
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Code
authors.forename: Sharon C
authors.initials: SC
authors.lastname: Caughey
authors.forename: Kevin
authors.initials: K
authors.lastname: Baker
authors.forename: James
authors.initials: J
authors.lastname: Watters
authors.forename: Jim
authors.initials: J
authors.lastname: Worthington
authors.forename: Carl
authors.initials: C
authors.lastname: van Walraven
mesh_terms: D000328:Adult; D000368:Aged; D000553:Ambulatory Care / Q000592:standards; D006784:Hospitals, Teaching / Q000592:standards* / Q000706:statistics & numerical data; D006801:Humans; D007049:Iatrogenic Disease / Q000453:epidemiology*; D015994:Incidence; D019300:Medical Errors / Q000706:statistics & numerical data; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D017751:Safety Management / Q000592:standards / Q000706:statistics & numerical data*; D013997:Time Factors