Evaluation of POSSUM and P-POSSUM scoring systems in assessing outcome after laparoscopic colectomy

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Abstract
Background The purpose of this study was to compare the actual and predicted risk-adjusted morbidity and mortality after laparoscopic colectomy (LAC) calculated using both the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) and Portsmouth POSSUM (P-POSSUM) scoring systems. Methods All patients who underwent LAC performed by a single surgeon between March 1999 and December 2000 were analysed. The observed morbidity and mortality rates were compared with those predicted by the POSSUM scoring system, and the observed mortality rate with that predicted by P-POSSUM. The operative severity component of the operative score was sequentially decreased from 4 (standard score for open colectomy) to 2, then 1, in an attempt to correct overprediction. Results Two hundred and fifty-one consecutive patients underwent LAC, with a conversion rate of 8·0 per cent. The morbidity rate (6·8 per cent) was significantly lower than the predicted rates calculated with an operative score of 4 or 2 (12·4 per cent, P < 0·001; 9·6 per cent, P = 0·001), but was fully corrected with an operative score of 1 (7·0 per cent, P = 0·325). The observed mortality rate (0·8 per cent) was significantly different from the expected mortality rates calculated using either uncorrected POSSUM (9·6 per cent, P = 0·001) or P-POSSUM (3·5 per cent, P = 0·001). POSSUM (2·6 per cent, P = 0·007) continued to overpredict mortality but P-POSSUM (1·0 per cent, P = 0·001) accurately predicted mortality with an operative score of 1. Conclusion LAC appeared to be associated with lower morbidity and mortality rates than those predicted by the POSSUM scoring system, and with a lower mortality rate than that predicted using the P-POSSUM system.

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