A Comparison of the P‐POSSUM and NELA Risk Score for Patients Undergoing Emergency Laparotomy in Singapore

BACKGROUND (AIMS, HYPOTHESES, OR OBJECTIVES): Emergency laparotomy (EL) is a high-risk surgical procedure associated with considerable morbidity and mortality around the world. A reliable risk-assessment tool that is specific to patients undergoing EL allows the early identification of high-risk patients and enables appropriate healthcare resource allocation. The objective of this study was to compare the commonly used Portsmouth-physiologic and operative severity score for the enumeration of mortality and morbidity (P-POSSUM) with the recently developed National Emergency Laparotomy Audit (NELA) score in terms of their accuracy for identifying patients at increased risk of 30-day mortality in a predominantly Asian population. METHODS: Physiological and operative data from a prospectively collected audit of adult patients undergoing EL in 2018 and 2019 across two tertiary hospitals in Singapore were used to retrospectively calculate both the P-POSSUM and NELA scores for each patient encounter. This was then compared to actual mortality rates to determine each model's accuracy and precision. RESULTS: 830 patients were included in the study with a 30-day mortality of 5.66%. The area under the receiver operating characteristics curve (AUROC) was similar for both the NELA (0.86, p < 0.001, 95% CI 0.81-0.91) and the P-POSSUM models (0.84, p < 0.001, 95% CI 0.78-0.89). While the models over-predicted mortality, overall O:E ratios showed that the NELA model performance was superior to that of P-POSSUM (0.58 95% CI 0.43-0.77 compared to 0.34 95% CI 0.26-0.46). CONCLUSION: The NELA risk-prediction model accurately predicts 30-day mortality in this large cohort of patients undergoing EL and outperforms the current P-POSSUM model. We recommend that the NELA score should replace the P-POSSUM score as a model to distinguish between high- and low-risk patients undergoing EL.