title: POSSUM and P-POSSUM overpredict mortality for carotid endarterectomy.
abstract: OBJECTIVE
  the aim was to test the predictive accuracy of POSSUM and P-POSSUM on patients undergoing CEA.
  
  
  METHODS
  retrospective and prospective study.
  
  
  METHODS
  499 CEAs performed by four vascular surgeons from a single unit from 1992-99. The median age was 68 (range 38-86) and 60% were men.
  
  
  METHODS
  physiological parameters, operative parameters and the 30-day mortality were collected. Predicted mortality for each patient was calculated using POSSUM and P-POSSUM equations. Patients were stratified into risk groups and observed and predicted deaths were compared. Accuracy of the prediction was assessed using chi-squared analysis.
  
  
  RESULTS
  the observed 30-day mortality was 1.8% (9/499). The predicted deaths using POSSUM and P-POSSUM analysis were 49 and 25 respectively compared to nine observed deaths. There was significant evidence of lack of fit of both models in predicting mortality (chi-squared analysis, p<0.05).
  
  
  CONCLUSIONS
  POSSUM and P-POSSUM overpredict mortality and are unsuitable for comparative audit of CEA. Models developed specific for CEA might accurately predict mortality.
authors.affiliation: Academic Vascular Unit, Hull Royal Infirmary, Hull, UK.
authors.forename: G
authors.initials: G
authors.lastname: Kuhan
authors.forename: A F
authors.initials: AF
authors.lastname: Abidia
authors.forename: L D
authors.initials: LD
authors.lastname: Wijesinghe
authors.forename: I C
authors.initials: IC
authors.lastname: Chetter
authors.forename: B F
authors.initials: BF
authors.lastname: Johnson
authors.forename: A R
authors.initials: AR
authors.lastname: Wilkinson
authors.forename: P M
authors.initials: PM
authors.lastname: Renwick
authors.forename: P T
authors.initials: PT
authors.lastname: McCollum
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002340:Carotid Artery Diseases / Q000401:mortality* / Q000601:surgery*; D016894:Endarterectomy, Carotid / Q000401:mortality*; D005260:Female; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012189:Retrospective Studies