title: Enhancing the Value of Population-Based Risk Scores for Institutional-Level Use.
abstract: BACKGROUND
  We hypothesized that factors associated with an institution's residual risk unaccounted for by population-based models may be identifiable and used to enhance the value of population-based risk scores for quality improvement.
  
  
  METHODS
  From January 2000 to January 2010, 4,971 patients underwent aortic valve replacement (AVR), either isolated (n = 2,660) or with concomitant coronary artery bypass grafting (AVR+CABG; n = 2,311). Operative mortality and major morbidity and mortality predicted by The Society of Thoracic Surgeons (STS) risk models were compared with observed values. After adjusting for patients' STS score, additional and refined risk factors were sought to explain residual risk. Differences between STS model coefficients (risk-factor strength) and those specific to our institution were calculated.
  
  
  RESULTS
  Observed operative mortality was less than predicted for AVR (1.6% [42 of 2,660] vs 2.8%, p < 0.0001) and AVR+CABG (2.6% [59 of 2,311] vs 4.9%, p < 0.0001). Observed major morbidity and mortality was also lower than predicted for isolated AVR (14.6% [389 of 2,660] vs 17.5%, p < 0.0001) and AVR+CABG (20.0% [462 of 2,311] vs 25.8%, p < 0.0001). Shorter height, higher bilirubin, and lower albumin were identified as additional institution-specific risk factors, and body surface area, creatinine, glomerular filtration rate, blood urea nitrogen, and heart failure across all levels of functional class were identified as refined risk-factor variables associated with residual risk. In many instances, risk-factor strength differed substantially from that of STS models.
  
  
  CONCLUSIONS
  Scores derived from population-based models can be enhanced for institutional level use by adjusting for institution-specific additional and refined risk factors. Identifying these and measuring differences in institution-specific versus population-based risk-factor strength can identify areas to target for quality improvement initiatives.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Sajjad
authors.initials: S
authors.lastname: Raza
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio. Electronic address: sabikj@ccf.org.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Sabik
authors.affiliation: Department of Quantitative Health Sciences, Research Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Jeevanantham
authors.initials: J
authors.lastname: Rajeswaran
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Jay J
authors.initials: JJ
authors.lastname: Idrees
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Matteo
authors.initials: M
authors.lastname: Trezzi
authors.affiliation: Department of Internal Medicine, Medicine Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Haris
authors.initials: H
authors.lastname: Riaz
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Hoda
authors.initials: H
authors.lastname: Javadikasgari
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Nowicki
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Lars G
authors.initials: LG
authors.lastname: Svensson
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Heart and Vascular Institute, Cleveland Clinic, Cleveland, Ohio; Department of Quantitative Health Sciences, Research Institute, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Eugene H
authors.initials: EH
authors.lastname: Blackstone
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000000981:diagnostic imaging / Q000601:surgery*; D001024:Aortic Valve Stenosis / Q000150:complications / Q000175:diagnosis / Q000601:surgery*; D017023:Coronary Angiography; D001026:Coronary Artery Bypass / Q000379:methods*; D003324:Coronary Artery Disease / Q000150:complications / Q000175:diagnosis / Q000601:surgery*; D004452:Echocardiography; D005260:Female; D005500:Follow-Up Studies; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000379:methods*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009820:Ohio / Q000453:epidemiology; D011183:Postoperative Complications / Q000453:epidemiology*; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D015996:Survival Rate / Q000639:trends; D016896:Treatment Outcome; D055815:Young Adult