title: Risk factors for and prediction of mortality in critically ill medical-surgical patients receiving heparin thromboprophylaxis.
abstract: BACKGROUND
  Previous studies have suggested that prediction models for mortality should be adjusted for additional risk factors beyond the Acute Physiology and Chronic Health Evaluation (APACHE) score. Our objective was to identify risk factors independent of APACHE II score and construct a prediction model to improve the predictive accuracy for hospital and intensive care unit (ICU) mortality.
  
  
  METHODS
  We used data from a multicenter randomized controlled trial (PROTECT, Prophylaxis for Thromboembolism in Critical Care Trial) to build a new prediction model for hospital and ICU mortality. Our primary outcome was all-cause 60-day hospital mortality, and the secondary outcome was all-cause 60-day ICU mortality.
  
  
  RESULTS
  We included 3746 critically ill non-trauma medical-surgical patients receiving heparin thromboprophylaxis (43.3 % females) in this study. The new model predicting 60-day hospital mortality incorporated APACHE II score (main effect: hazard ratio (HR) = 0.97 for per-point increase), body mass index (BMI) (main effect: HR = 0.92 for per-point increase), medical admission versus surgical (HR = 1.67), use of inotropes or vasopressors (HR = 1.34), acetylsalicylic acid or clopidogrel (HR = 1.27) and the interaction term between APACHE II score and BMI (HR = 1.002 for per-point increase). This model had a good fit to the data and was well calibrated and internally validated. However, the discriminative ability of the prediction model was unsatisfactory (C index < 0.65). Sensitivity analyses supported the robustness of these findings. Similar results were observed in the new prediction model for 60-day ICU mortality which included APACHE II score, BMI, medical admission and invasive mechanical ventilation.
  
  
  CONCLUSIONS
  Compared with the APACHE II score alone, the new prediction model increases data collection, is more complex but does not substantially improve discriminative ability.
  
  
  BACKGROUND
  ClinicalTrials.gov Identifier: NCT00182143.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.
authors.forename: Guowei
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.|Centre for Evaluation of Medicines, St. Joseph's Healthcare Hamilton, McMaster University, 25 Main St. West, Suite 2000, 20th Floor, Hamilton, ON, L8P 1H1, Canada.
authors.forename: Lehana
authors.initials: L
authors.lastname: Thabane
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.|Centre for Evaluation of Medicines, St. Joseph's Healthcare Hamilton, McMaster University, 25 Main St. West, Suite 2000, 20th Floor, Hamilton, ON, L8P 1H1, Canada.|Department of Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Cook
authors.affiliation: Duke Clinical Research Institute, Duke University, Durham, NC, USA.
authors.forename: Renato D
authors.initials: RD
authors.lastname: Lopes
authors.affiliation: Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, ON, Canada.|Critical Care Medicine, St. Michael's Hospital, Toronto, ON, Canada.
authors.forename: John C
authors.initials: JC
authors.lastname: Marshall
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.|Department of Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Gordon
authors.initials: G
authors.lastname: Guyatt
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.|Centre for Evaluation of Medicines, St. Joseph's Healthcare Hamilton, McMaster University, 25 Main St. West, Suite 2000, 20th Floor, Hamilton, ON, L8P 1H1, Canada.|Department of Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Anne
authors.initials: A
authors.lastname: Holbrook
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.|School of Nursing, McMaster University, Hamilton, ON, Canada.
authors.forename: Noori
authors.initials: N
authors.lastname: Akhtar-Danesh
authors.affiliation: Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, ON, Canada.|Department of Critical Care Medicine, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Fowler
authors.affiliation: Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, ON, Canada.|Department of Critical Care Medicine, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors.forename: Neill K J
authors.initials: NKJ
authors.lastname: Adhikari
authors.affiliation: Mercy Clinic Adult Critical Care, Mercy Hospital Saint Louis, Saint Louis, MO, USA.
authors.forename: Rob
authors.initials: R
authors.lastname: Taylor
authors.affiliation: King Saud bin Abdulaziz University for Health Sciences and King Abdullah International Medical Research Center, Riyadh, Saudi Arabia.
authors.forename: Yaseen M
authors.initials: YM
authors.lastname: Arabi
authors.affiliation: Critical Care Medicine, Vancouver Coastal Health Research Institute, Vancouver, BC, Canada.
authors.forename: Dean
authors.initials: D
authors.lastname: Chittock
authors.affiliation: Center for Health Evaluation and Outcome Sciences and Division of Critical Care Medicine, St. Paul's Hospital and University of British Columbia, Vancouver, BC, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Dodek
authors.affiliation: Department of Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Andreas P
authors.initials: AP
authors.lastname: Freitag
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Walter
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.
authors.forename: Diane
authors.initials: D
authors.lastname: Heels-Ansdell
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada. levinem@mcmaster.ca.|Centre for Evaluation of Medicines, St. Joseph's Healthcare Hamilton, McMaster University, 25 Main St. West, Suite 2000, 20th Floor, Hamilton, ON, L8P 1H1, Canada. levinem@mcmaster.ca.|Department of Medicine, McMaster University, Hamilton, ON, Canada. levinem@mcmaster.ca.
authors.forename: Mitchell A H
authors.initials: MAH
authors.lastname: Levine
keywords: APACHE; Critical care; Intensive care unit; Mortality; Prediction model