Evaluation of POSSUM and P-POSSUM scoring systems in patients undergoing colorectal surgery

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). Conclusion: 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. Copyright © 2002 British Journal of Surgery Society Ltd. Published by John Wiley & Sons Ltd Both systems underestimate mortality in the elderly and in emergency surgery