title: Predicting post-operative mortality in patients undergoing colorectal surgery using P-POSSUM and CR-POSSUM scores: a prospective study.
abstract: BACKGROUND
  POSSUM and its variants Portsmouth POSSUM (P-POSSUM) and Colorectal POSSUM (CR-POSSUM) equations were derived from a heterogeneous general surgical population, which have been used successfully to provide risk-adjusted operative mortality rates. CR-POSSUM utilises fewer parameters, allowing ease of use. The aim of this study was to predict the mortality outcome in colorectal surgery using these scoring systems compared to the observed mortality and to devise a new scoring system with improved accuracy.
  
  
  METHODS
  The study was conducted prospectively on all consecutive patients requiring elective and emergency colorectal surgery between April 2002 and May 2005. The outcome parameter was defined as 30-day mortality. The observed mortality was compared with predicted mortality by the scoring systems. Hosmer and Lemeshow test was used to assess statistical accuracy of POSSUM.
  
  
  RESULTS
  Eight hundred ninety-nine patients underwent colorectal surgery during the study period. There were 619 elective and 281 emergency patients. Observed 30-day mortality rate was 9%, compared with predicted mortality rate of 13.5% with POSSUM, 5% with P-POSSUM and 9.5% with CR-POSSUM.
  
  
  CONCLUSIONS
  POSSUM's mortality rate was overestimated, while P-POSSUM's mortality rate was underestimated. CR-POSSUM, the simplest system of all three, most accurately predicted mortality in our unit.
authors.affiliation: Department of Surgery, University Hospitals Coventry and Warwickshire, Warwick, UK. ed.leung@doctors.org.uk
authors.forename: Edmund
authors.initials: E
authors.lastname: Leung
authors.forename: Ali M
authors.initials: AM
authors.lastname: Ferjani
authors.forename: Nigel
authors.initials: N
authors.lastname: Stellard
authors.forename: Ling S
authors.initials: LS
authors.lastname: Wong
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D003107:Colorectal Surgery / Q000401:mortality*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000401:mortality*; D011446:Prospective Studies; D012307:Risk Factors