Evaluation of POSSUM and P-POSSUM scoring systems for predicting the mortality in elective neurosurgical patients

Abstract

A simple way of evaluating surgical outcomes is to compare mortality and morbidity. Such comparisons may be misleading without a proper case mix. The POSSUM scoring system was developed to overcome this problem. The score can be used to derive predictive mortality and morbidity for surgical procedures. POSSUM and a modified version P-POSSUM have been evaluated in various groups of surgical patients for the accuracy of predicting mortality. These scoring systems have not been evaluated in neurosurgical patients. Thus, we tried to evaluate the usefulness of POSSUM and P-POSSUM scoring systems in neurosurgical patients in predicting in-hospital mortality. POSSUM physiological and operative variables were collected from all neurosurgical patients undergoing elective craniotomy, from April 2005 to Feb 2006. In-hospital mortality was obtained from the hospital mortality register. The physiological score, operative score, POSSUM predicted mortality rate and P-POSSUM predicted mortality rate were calculated using a calculator. The observed number of deaths was compared against the predicted deaths. A total of 285 patients with a mean age of 38 ± 15 years were studied. Overall observed mortality was nine patients (3.16%). The mortality predicted by the P-POSSUM model was also nine patients (3.16%). Mortality predicted by POSSUM was poor with predicted deaths in 31 patients (11%). The difference between observed and predicted deaths at different risk levels was not significant with P-POSSUM (p = 0.424) and was significantly different with POSSUM score (p < 0.001). P-POSSUM scoring system was highly accurate in predicting the overall mortality in neurosurgical patients. In contrast, POSSUM score was not useful for prediction of mortality.