Comparison of POSSUM and P-POSSUM for risk-adjusted audit of patients undergoing emergency laparotomy.

BACKGROUND: The Physiological and Operative Severity Score for Enumeration of Mortality and Morbidity (POSSUM) scoring system, derived from a heterogeneous population, has been used successfully as an audit tool, but it has appeared to over-predict mortality in low-risk groups for which an alternative system, the Portsmouth predictor equation for mortality (P-POSSUM) was designed and used successfully. In this prospective study, we compared these two equations in predicting death and tested their validity in predicting morbidity and mortality in patients undergoing emergency laparotomy in a tertiary hospital.
METHODS: Eighty-two patients who underwent emergency laparotomy were included in this study. Actual morbidity and mortality rates were compared with the predicted mortality and morbidity rates using both POSSUM and P-POSSUM equations by linear regression and exponential methods of analysis.
RESULTS: POSSUM equation significantly over-predicted both morbidity and mortality when linear regression analysis was used, but predicted well when exponential analysis was used. Prediction of mortality by P-POSSUM was good using both linear and exponential analyses, and exponential method was better than linear regression analysis.
CONCLUSION: P-POSSUM is a better equation than POSSUM in predicting mortality, and exponential method is better than linear regression analysis. Both equations are useful tools for risk-adjusted surgical audit of patients undergoing emergency laparotomy.