title: Comparison of P-POSSUM risk-adjusted mortality rates after surgery between patients in the USA and the UK.
abstract: BACKGROUND
  The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) criteria have been used to assess surgical risk in patients in the UK. The aim was to determine how applicable these criteria are to patients undergoing surgery in the USA.
  
  
  METHODS
  Two cohorts of patients undergoing major non-cardiac surgery were followed prospectively in the USA (n = 1056) and the UK (n = 1539). Each patient was assigned a risk score for preoperative physiological status and operative severity using the established POSSUM criteria. Death in hospital was the primary outcome measure. For each patient a predicted risk of death was calculated from Portsmouth POSSUM (P-POSSUM) methodology using an established equation. The relationships between predicted and observed mortality rates in each cohort were investigated by means of multivariate logistic regression.
  
  
  RESULTS
  Within each cohort, an increase in risk estimated by P-POSSUM predicted an increase in observed mortality rate (P < 0.001). For any given risk level, however, mortality rates were significantly higher in the UK cohort than in the US cohort (odds ratio 4.50 (95 per cent confidence interval 2.81 to 7.19); Z = 6.25, P < 0.001).
  
  
  CONCLUSIONS
  An increase in predicted risk, based on the P-POSSUM methodology, was associated with a higher mortality rate in patients from both countries. However, risk-adjusted mortality rates following major surgery were four times higher in the UK cohort. These marked differences warrant validation in a larger number of centres.
authors.affiliation: Department of Anesthesiology, Columbia University College of Physicians and Surgeons, Columbia University Mailman School of Public Health, New York, USA. benne011@mc.duke.edu
authors.forename: E
authors.initials: E
authors.lastname: Bennett-Guerrero
authors.forename: J A
authors.initials: JA
authors.lastname: Hyam
authors.forename: S
authors.initials: S
authors.lastname: Shaefi
authors.forename: D R
authors.initials: DR
authors.lastname: Prytherch
authors.forename: G L
authors.initials: GL
authors.lastname: Sutton
authors.forename: P C
authors.initials: PC
authors.lastname: Weaver
authors.forename: M G
authors.initials: MG
authors.lastname: Mythen
authors.forename: M P
authors.initials: MP
authors.lastname: Grocott
authors.forename: M K
authors.initials: MK
authors.lastname: Parides
mesh_terms: D015331:Cohort Studies; D006801:Humans; D011183:Postoperative Complications / Q000401:mortality*; D011237:Predictive Value of Tests; D012044:Regression Analysis; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D016019:Survival Analysis; D015996:Survival Rate; D006113:United Kingdom / Q000453:epidemiology; D014481:United States / Q000453:epidemiology