Comparison of POSSUM with P-POSSUM for Prediction of Mortality in Infrarenal Abdominal Aortic Aneurysm Repair

The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) is a simple and valid scoring system in predicting mortality and morbidity rates. The Portsmouth predictor equation (P-POSSUM) has been shown to be a more accurate predictor of death than the POSSUM in vascular patients. The length of hospital stay (LOS) equation has been suggested to be of value in predicting total length of stay. The aim of this study was to test the validity of the POSSUM, P-POSSUM, and LOS in predicting outcome of patients undergoing abdominal aortic aneurysm (AAA) repair. POSSUM scores in 118 patients who underwent AAA repair by a single consultant were recorded retrospectively. Observed rates of mortality, morbidity, and length of hospital stay were correlated with the rates predicted by POSSUM, P-POSSUM, and LOS equations in three groups: all cases, 93 elective repairs, and emergency AAA repairs. The POSSUM and the P-POSSUM performed similarly in terms of accuracy of prediction, with all predicted values being not significantly different from those observed. The POSSUM tended to overpredict mortality compared to the P-POSSUM. The POSSUM predicted morbidity well. The LOS equation failed to predict significantly observed total hospital stay. POSSUM and P-POSSUM outcome risk equations are thus valid in predicting mortality for all cases and emergency AAA repairs. The POSSUM morbidity equation predicts complications quantitatively.