title: Adjustment of intensive care unit outcomes for severity of illness and comorbidity scores.
abstract: OBJECTIVE
  Comparison of outcomes among intensive care units (ICUs) requires adjustment for patient variables. Severity of illness scores are associated with hospital mortality, but administrative databases rarely include the elements of these scores. However, these databases include the elements of comorbidity scores. The purpose of this study was to compare the value of these scores as adjustment variables in statistical models of hospital mortality and hospital and ICU length of stay after adjustment for other covariates.
  
  
  METHODS
  We used multivariable regression to study 1808 patients admitted to a 13-bed medical-surgical ICU in a 400-bed tertiary hospital between December 1998 and August 2003.
  
  
  RESULTS
  For all patients, after adjusting for age, sex, major clinical category, source of admission, and socioeconomic determinants of health, we found that Acute Physiology and Chronic Health Evaluation (APACHE) II and comorbidity scores were significantly associated with hospital mortality and that comorbidity but not APACHE II was significantly associated with hospital length of stay. Separate analysis of hospital survivors and nonsurvivors showed that both APACHE II and comorbidity scores were significantly associated with hospital length of stay and APACHE II score was associated with ICU length of stay.
  
  
  CONCLUSIONS
  The value of APACHE II and comorbidity scores as adjustment variables depends on the outcome and population of interest.
authors.affiliation: Center for Health Evaluation and Outcome Sciences, St Paul's Hospital and University of British Columbia, Vancouver, B.C., Canada V6Z 1Y6.
authors.forename: Monica
authors.initials: M
authors.lastname: Norena
authors.forename: Hubert
authors.initials: H
authors.lastname: Wong
authors.forename: Willie D
authors.initials: WD
authors.lastname: Thompson
authors.forename: Sean P
authors.initials: SP
authors.lastname: Keenan
authors.forename: Peter M
authors.initials: PM
authors.lastname: Dodek
mesh_terms: D018806:APACHE; D000328:Adult; D000368:Aged; D001955:British Columbia; D015897:Comorbidity; D003325:Coronary Care Units / Q000706:statistics & numerical data; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012959:Socioeconomic Factors; D016896:Treatment Outcome