Validation of long-term survival prediction for scheduled abdominal aortic aneurysm repair with an independent calculator using only pre-operative variables

We observed survival after scheduled repair of abdominal aortic aneurysm in 1096 patients for a median (IQR [range]) of 3.0 (1.5-5.8 [0-15])years: 943 patients had complete data, 250 of whom died. We compared discrimination and calibration of an external model with the Kaplan-Meier model generated from the study data. Integrated Brier misclassification scores for both models at 1-5 postoperative years were 0.04, 0.08, 0.11, 0.13 and 0.16, respectively. Harrel's concordance index at 1-5 postoperative years was 0.73, 0.71, 0.68, 0.67 and 0.66, respectively. Groups with median 5-year predicted mortality of 40% (n=251), 18% (n=414) and 8% (n=164) had lower observed mortality than 114 patients with 70% predicted mortality, hazard ratio (95% CI): 0.58 (0.37-0.76), p=0.0031; 0.30 (0.19-0.48), p=1.7x10(-12) and 0.19 (0.13-0.27), p=1.3x10(-10), respectively, test for trend p=5.6x10(-15). Survival predicted by the external calculator was similar to the Kaplan-Meier estimate.