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 = 1.7 × 10(-12) and 0.19 (0.13-0.27), p = 1.3 × 10(-10) , respectively, test for trend p = 5.6 × 10(-15) . Survival predicted by the external calculator was similar to the Kaplan-Meier estimate.