title: Comparison of P-POSSUM and O-POSSUM in predicting mortality after oesophagogastric resections.
abstract: BACKGROUND
  P-POSSUM (Physiological and Operative Severity Score for the enumeration of Mortality and morbidity) predicts mortality and morbidity in general surgical patients providing an adjunct to surgical audit. O-POSSUM was designed specifically to predict mortality and morbidity in patients undergoing oesophagogastric surgery.
  
  
  OBJECTIVE
  To compare P-POSSUM and O-POSSUM in predicting surgical mortality in patients undergoing elective oesophagogastric cancer resections.
  
  
  METHODS
  Elective oesophagogastric cancer resections in a district general hospital from 1990 to 2002 were scored by P-POSSUM and O-POSSUM methods. Observed mortality rates were compared to predicted mortality rates in six risk groups for each model using the Hosmer-Lemeshow goodness-of-fit test. The power to discriminate between patients who died and those who survived was assessed using the area under the receiver-operator characteristic (ROC) curve.
  
  
  RESULTS
  313 patients underwent oesophagogastric resections. 32 died within 30 days (10.2%). P-POSSUM predicted 36 deaths (chi2 = 15.19, df = 6, p = 0.019, Hosmer-Lemeshow goodness-of-fit test), giving a standardised mortality ratio (SMR) of 0.89. O-POSSUM predicted 49 deaths (chi2 = 16.51, df = 6, p = 0.011), giving an SMR of 0.65. The area under the ROC curve was 0.68 (95% confidence interval 0.59 to 0.76) for P-POSSUM and 0.61 (95% confidence interval 0.50 to 0.72) for O-POSSUM.
  
  
  CONCLUSIONS
  Neither model accurately predicted the risk of postoperative death. P-POSSUM provided a better fit to observed results than O-POSSUM, which overpredicted total mortality. P-POSSUM also had superior discriminatory power.
authors.affiliation: Department of Surgery, Crosshouse Hospital, Kilmarnock, UK. nags1970@aol.com
authors.forename: J S
authors.initials: JS
authors.lastname: Nagabhushan
authors.forename: S
authors.initials: S
authors.lastname: Srinath
authors.forename: F
authors.initials: F
authors.lastname: Weir
authors.forename: W J
authors.initials: WJ
authors.lastname: Angerson
authors.forename: B A
authors.initials: BA
authors.lastname: Sugden
authors.forename: C G
authors.initials: CG
authors.lastname: Morran
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004938:Esophageal Neoplasms / Q000401:mortality / Q000601:surgery*; D016629:Esophagectomy / Q000401:mortality*; D005260:Female; D005743:Gastrectomy / Q000401:mortality*; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000401:mortality; D012372:ROC Curve; D018570:Risk Assessment; D012720:Severity of Illness Index; D013274:Stomach Neoplasms / Q000401:mortality / Q000601:surgery*