Table 3. Pairwise comparison of the AUC for the three mortality scores against observed 30-day and 90-day mortality.

AUC = area under the curve; Std. Error = standard error; CI = confidence interval; Pre-op = preoperative; Post-op = postoperative; NELA = National Emergency Laparotomy Audit; P-POSSUM = Portsmouth Physiological and Operative Severity Score for the enumeration of Mortality and Morbidity

	Difference between areas	Std. error	95% CI		Z statistic	P-value
			Lower bound	Upper bound
30-day mortality
Pre-op NELA vs. Pre-op P-Possum	0.00716	0.0134	-0.0191	0.0335	0.533	0.5938
Pre-op NELA vs. Post-op NELA	0.0299	0.0229	-0.0149	0.0748	1.309	0.1906
Pre-op P-Possum vs. Post-op NELA	0.0228	0.0215	-0.0194	0.0650	1.058	0.2899
90-day mortality
Pre-op NELA vs. Pre-op P-Possum	0.0154	0.0112	-0.00659	0.0373	1.372	0.1702
Pre-op NELA vs. Post-op NELA	0.0191	0.0198	-0.0197	0.0579	0.963	0.3353
Pre-op P-Possum vs. Post-op NELA	0.00373	0.0199	-0.0352	0.0427	0.188	0.8509