POSSUM and P-POSSUM as Predictors of Postoperative Morbidity and Mortality in Patients Undergoing Hepato-biliary-pancreatic Surgery: A Meta-analysis

Abstract

Physiologic and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) models are used extensively to predict postoperative morbidity and mortality in general surgery. The aim was to undertake the first meta-analysis of the predictive value of these models in patients undergoing hepato-biliary-pancreatic surgery. Eligible articles were identified by searches of electronic databases from 1991 to 2012. All data were specific to hepato-biliary-pancreatic surgery. Predictive value of morbidity and mortality were assessed by calculating weighted observed to expected (O/E) ratios. Subanalysis was also performed. Sixteen studies were included in final review. The morbidity analysis included nine studies on POSSUM with a weighted O/E ratio of 0.78 [95% confidence interval (CI) 0.68-0.88]. The mortality analysis included seven studies on POSSUM and nine studies on P-POSSUM (Portsmouth predictor equation for mortality). Weighted O/E ratios for mortality were 0.35 (95% CI 0.17-0.54) for POSSUM and 0.95 (95% CI 0.65-1.25) for P-POSSUM. POSSUM had more accuracy to predict morbidity after pancreatic surgery (O/E ratio 0.82; 95% CI 0.72-0.92) than after hepatobiliary surgery (O/E ratio 0.66; 95% CI 0.57-0.74), in large sample size studies (O/E ratio 0.90; 95% CI 0.85-0.96) than in small sample size studies (O/E ratio 0.69; 95% CI 0.59-0.79). POSSUM overpredicted postoperative morbidity after hepato-biliary-pancreatic surgery. Predictive value of POSSUM to morbidity was affected by the type of surgery and the sample size of studies. Compared with POSSUM, P-POSSUM was more accurate for predicting postoperative mortality. Modifications to POSSUM and P-POSSUM are needed for audit in hepato-biliary-pancreatic surgery.