Risk adjustment for audit of low risk general surgical patients by Jabalpur-POSSUM score

INTRODUCTION: Physiological and Operative Severity Score for enUmeration of Mortality and morbidity (POSSUM) and its Portsmouth modification (P-POSSUM) were developed to provide risk-adjusted analysis in patients undergoing surgery; but have not been validated in low-risk patients. The aim of this study was to assess POSSUM and P-POSSUM in general surgical patients in a developing country.
MATERIALS AND METHODS: Seven hundred and eighty-eight consecutive general surgical patients were studied prospectively with POSSUM and P-POSSUM scoring systems using linear and exponential analysis. The ratio of observed to predicted death and morbidity (0: E) was calculated for each analysis and frequency tables were compared for statistical significance by means of chi square test. In the second part of this study prospective evaluation of Modified POSSUM was performed on the next 908 patients.
RESULTS: POSSUM was found to be a good predictor of mortality and morbidity with exponential analysis but not with linear analysis. P-POSSUM predicted the mortality accurately with the help of linear analysis. Both overpredicted the outcome in the low-risk group (predicted risk of mortality < 10% and predicted risk of morbidity < 40%); therefore POSSUM needs to be modified for audit in the low-risk group. Such a modification, Jabalpur-POSSUM (J-POSSUM: a modification of POSSUM for low-risk group) revealed good fitness with observed mortality (O: E = 1.00) and morbidity (O: E = 1.04). On prospective evaluation of J-POSSUM, this finding was confirmed for the low-risk group vis-à-vis observed mortality (O: E = 1.16) and morbidity (O: E = 0.83).
CONCLUSION: POSSUM is not a good predictor of low-risk patients and needs risk adjustment with the help of correcting factor for accurately predicting the mortality and morbidity. Such a correction factor was identified with the help of multiple logistic regression analysis and prospectively validated. Jabalpur-POSSUM can successfully predict the outcome in low-risk patients.