title: Gaming in risk-adjusted mortality rates: effect of misclassification of risk factors in the benchmarking of cardiac surgery risk-adjusted mortality rates.
abstract: OBJECTIVE
  Upcoding or undercoding of risk factors could affect the benchmarking of risk-adjusted mortality rates. The aim was to investigate the effect of misclassification of risk factors on the benchmarking of mortality rates after cardiac surgery.
  
  
  METHODS
  A prospective cohort was used comprising all adult cardiac surgery patients in all 16 cardiothoracic centers in The Netherlands from January 1, 2007, to December 31, 2009. A random effects model, including the logistic European system for cardiac operative risk evaluation (EuroSCORE) was used to benchmark the in-hospital mortality rates. We simulated upcoding and undercoding of 5 selected variables in the patients from 1 center. These patients were selected randomly (nondifferential misclassification) or by the EuroSCORE (differential misclassification).
  
  
  RESULTS
  In the random patients, substantial misclassification was required to affect benchmarking: a 1.8-fold increase in prevalence of the 4 risk factors changed an underperforming center into an average performing one. Upcoding of 1 variable required even more. When patients with the greatest EuroSCORE were upcoded (ie, differential misclassification), a 1.1-fold increase was sufficient: moderate left ventricular function from 14.2% to 15.7%, poor left ventricular function from 8.4% to 9.3%, recent myocardial infarction from 7.9% to 8.6%, and extracardiac arteriopathy from 9.0% to 9.8%.
  
  
  CONCLUSIONS
  Benchmarking using risk-adjusted mortality rates can be manipulated by misclassification of the EuroSCORE risk factors. Misclassification of random patients or of single variables will have little effect. However, limited upcoding of multiple risk factors in high-risk patients can greatly influence benchmarking. To minimize "gaming," the prevalence of all risk factors should be carefully monitored.
authors.affiliation: Department of Cardiothoracic Surgery, University Medical Center Utrecht, Utrecht, The Netherlands. s.siregar@umcutrecht.nl
authors.forename: Sabrina
authors.initials: S
authors.lastname: Siregar
authors.forename: Rolf H H
authors.initials: RH
authors.lastname: Groenwold
authors.forename: Michel I M
authors.initials: MI
authors.lastname: Versteegh
authors.forename: Luc
authors.initials: L
authors.lastname: Noyez
authors.forename: Willem Jan P P
authors.initials: WJ
authors.lastname: ter Burg
authors.forename: Michiel L
authors.initials: ML
authors.lastname: Bots
authors.forename: Yolanda
authors.initials: Y
authors.lastname: van der Graaf
authors.forename: Lex A
authors.initials: LA
authors.lastname: van Herwerden
mesh_terms: D000328:Adult; D000368:Aged; D019985:Benchmarking; D006348:Cardiac Surgical Procedures / Q000401:mortality*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D014652:Vascular Diseases / Q000401:mortality; D018487:Ventricular Dysfunction, Left / Q000401:mortality