POSSUM and p-POSSUM overestimate morbidity and mortality in laparoscopic bariatric surgery

Despite their wide use in surgical audit, the application of the Physiologic and Operative Severity Score for the enUmeration of Mortality and Morbidity (POSSUM) and the Portsmouth predictor of mortality (p-POSSUM) in bariatric surgery has been limited. The aim of this study was to evaluate the usefulness of POSSUM and p-POSSUM in bariatric comparative audit.

Data were retrospectively collected on consecutive patients who underwent laparoscopic gastric by-pass (LRYGB) and sleeve gastrectomy (SG) at a teaching institute. POSSUM and p-POSSUM equations were applied. The observed to expected ratios for morbidity and mortality were calculated. A Student's t test was performed to assess if a relationship could be found between the observed and the predicted outcomes.

Between 2008 and 2013, 504 patients (370 female) with a mean (range) age of 46 (17-69) years underwent LRYGB (n = 383) and SG (n = 121). The operative morbidity was 10.9% and mortality was .2%. POSSUM overpredicted morbidity (30.56%), and no relationship between morbidity risk and the development of complications was found (P = .152). There was a grouping of patients in the low-risk mortality groups for both POSSUM and p-POSSUM. Both equations overpredicted mortality (5.95% and 1.62%, respectively).

Both POSSUM and p-POSSUM equations overpredicted morbidity and mortality in this only study in the literature of modern bariatric practice that employed a large representative patient sample receiving the commonest procedures. A multicenter study is needed to address the low incidence of events and enable modification of those equations for use in bariatric surgical audit.