title: A comparative study of four intensive care outcome prediction models in cardiac surgery patients.
abstract: BACKGROUND
  Outcome prediction scoring systems are increasingly used in intensive care medicine, but most were not developed for use in cardiac surgery patients. We compared the performance of four intensive care outcome prediction scoring systems (Acute Physiology and Chronic Health Evaluation II [APACHE II], Simplified Acute Physiology Score II [SAPS II], Sequential Organ Failure Assessment [SOFA], and Cardiac Surgery Score [CASUS]) in patients after open heart surgery.
  
  
  METHODS
  We prospectively included all consecutive adult patients who underwent open heart surgery and were admitted to the intensive care unit (ICU) between January 1st 2007 and December 31st 2008. Scores were calculated daily from ICU admission until discharge. The outcome measure was ICU mortality. The performance of the four scores was assessed by calibration and discrimination statistics. Derived variables (Mean- and Max- scores) were also evaluated.
  
  
  RESULTS
  During the study period, 2801 patients (29.6% female) were included. Mean age was 66.9 ± 10.7 years and the ICU mortality rate was 5.2%. Calibration tests for SOFA and CASUS were reliable throughout (p-value not < 0.05), but there were significant differences between predicted and observed outcome for SAPS II (days 1, 2, 3 and 5) and APACHE II (days 2 and 3). CASUS, and its mean- and maximum-derivatives, discriminated better between survivors and non-survivors than the other scores throughout the study (area under curve ≥ 0.90). In order of best discrimination, CASUS was followed by SOFA, then SAPS II, and finally APACHE II. SAPS II and APACHE II derivatives had discrimination results that were superior to those of the SOFA derivatives.
  
  
  CONCLUSIONS
  CASUS and SOFA are reliable ICU mortality risk stratification models for cardiac surgery patients. SAPS II and APACHE II did not perform well in terms of calibration and discrimination statistics.
authors.affiliation: Department of Cardiothoracic Surgery, Friedrich-Schiller-University of Jena, Jena, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Doerr
authors.forename: Akmal Ma
authors.initials: AM
authors.lastname: Badreldin
authors.forename: Matthias B
authors.initials: MB
authors.lastname: Heldwein
authors.forename: Torsten
authors.initials: T
authors.lastname: Bossert
authors.forename: Markus
authors.initials: M
authors.lastname: Richter
authors.forename: Thomas
authors.initials: T
authors.lastname: Lehmann
authors.forename: Ole
authors.initials: O
authors.lastname: Bayer
authors.forename: Khosro
authors.initials: K
authors.lastname: Hekmat
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006348:Cardiac Surgical Procedures; D005260:Female; D005500:Follow-Up Studies; D005858:Germany / Q000453:epidemiology; D006331:Heart Diseases / Q000401:mortality / Q000601:surgery*; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D007362:Intensive Care Units / Q000592:standards*; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011446:Prospective Studies; D012720:Severity of Illness Index; D055815:Young Adult