title: Evaluation of POSSUM and P-POSSUM scoring systems in patients undergoing colorectal surgery.
abstract: BACKGROUND
  The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) and Portsmouth POSSUM (P-POSSUM) equations were derived from a heterogeneous general surgical population and have been used successfully as audit tools to provide risk-adjusted operative mortality rates. Their applicability to high-risk emergency colorectal operations has not been established.
  
  
  METHODS
  POSSUM variables were recorded for 1017 patients undergoing major elective (n = 804) or emergency (n = 213) colorectal surgery in ten hospitals. Subgroup analysis was performed to investigate the predictive capability of POSSUM and P-POSSUM in emergency and elective surgery and in patients in different age groups.
  
  
  RESULTS
  The overall operative mortality rate was 7.5 per cent (POSSUM-estimated mortality rate 8.2 per cent; P-POSSUM-estimated mortality rate 7.1 per cent). In-hospital deaths increased exponentially with age. Both scoring systems overpredicted mortality in young patients and underpredicted mortality in the elderly (P < 0.001). Death was underpredicted by both systems for emergency cases, significantly so at a simulated emergency caseload of 47.9 per cent (P < 0.05).
  
  
  CONCLUSIONS
  There is a lack of calibration of POSSUM and P-POSSUM systems at the extremes of age and high emergency workload. This has important implication in clinical practice, as consultants with a high emergency workload may seem to underperform when these scoring systems are applied. Recalibration or remodelling strategies may facilitate the application of POSSUM-based systems in colorectal surgery.
authors.affiliation: Academic Department of Surgery, King's College Hospital, London, UK. ptekkis@blueyonder.co.uk
authors.forename: P P
authors.initials: PP
authors.lastname: Tekkis
authors.forename: N
authors.initials: N
authors.lastname: Kessaris
authors.forename: H M
authors.initials: HM
authors.lastname: Kocher
authors.forename: J D
authors.initials: JD
authors.lastname: Poloniecki
authors.forename: J
authors.initials: J
authors.lastname: Lyttle
authors.forename: A C J
authors.initials: AC
authors.lastname: Windsor
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000401:mortality / Q000601:surgery*; D003107:Colorectal Surgery / Q000401:mortality*; D005069:Evaluation Studies as Topic; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D012720:Severity of Illness Index