Estimation of mortality and morbidity risk in vascular surgery using POSSUM and the Portsmouth predictor equation

Background: The Physiological and Operative Severity Score for enUmeration of Mortality and morbidity (POSSUM) is a simple scoring system previously validated in general surgical patients which enables estimation of the risk of complications and death after operation. The Portsmouth predictor equation (P-POSSUM) is a modification that may result in more accurate prediction of death than POSSUM. The aim of this study was to test the validity of POSSUM and P-POSSUM in patients undergoing major arterial surgery in a specialist unit. Methods: Physiological and operative severity scores in 221 patients undergoing elective and emergency arterial surgery in a pure vascular practice under a single consultant were recorded prospectively. Observed morbidity and mortality rates were compared with the rates predicted by POSSUM and P-POSSUM using a linear method of analysis. Results: The POSSUM equation overestimated deaths with this analysis but the mortality rate estimated by P-POSSUM was not significantly different from the observed death rate. The risk of morbidity predicted by POSSUM was not significantly different from the observed complication rate. Conclusion: The POSSUM methodology combined with the P-POSSUM adjustment for death allows satisfactory prediction of mortality and morbidity rates in patients undergoing vascular surgery.