Predictive Performance of NELA Versus P-POSSUM Mortality Scores: Are We Underestimating the Risk of Mortality Following Emergency Laparotomy?

Background In this study, we aimed to compare the performance of the National Emergency Laparotomy Audit (NELA) and Portsmouth Physiological and Operative Severity Score for the enumeration of Mortality and Morbidity (P-POSSUM) mortality risk scores in predicting 30-day and 90-day mortality in patients undergoing emergency laparotomy. Methodology A retrospective cohort study was conducted to compare the predictive performance of preoperative NELA, postoperative NELA, and P-POSSUM predicted mortality scores in patients undergoing emergency laparotomy between 2014 and 2021. The outcomes of interest included the observed 30-day and 90-day mortality. The discrimination of the mortality tools was assessed and compared by determining the area under the curve (AUC) for each tool using the receiver operating characteristic curve analysis. Results A total of 681 patients were included. The observed risk of 30-day and 90-day mortality was 10.4% (71/681) and 14.2% (97/681), respectively. Regarding 30-day mortality, the AUC was 0.791 (0.727-0.855) for the preoperative NELA score, 0.784 (0.721-0.848) for the preoperative P-POSSUM score, and 0.761 (0.699-0.824) for the postoperative NELA score. Regarding 90-day mortality, the AUC was 0.765 (0.708-0.821) for the preoperative NELA score, 0.749 (0.692-0.807) for the preoperative P-POSSUM score, and 0.745 (0.691-0.800) for the postoperative NELA score. The observed/expected ratio for 30-day and 90-day mortality was 3.25 and 4.43 for preoperative NELA, 2.81 and 3.84 for preoperative P-POSSUM, and 2.17 and 2.96 for postoperative NELA, respectively. Pairwise comparisons showed no statistically significant difference in discrimination among the three models. Conclusions Preoperative NELA, postoperative NELA, and P-POSSUM scores underestimated the risk of 30-day and 90-day mortality in patients undergoing emergency laparotomy. No significant difference in predictive performance was found among the three models.