Comparison of mortality prediction models after open abdominal aortic aneurysm repair

Objectives. Comparison of the accuracy of prediction of contemporary mortality prediction models after open Abdominal Aortic Aneurysm (AAA) surgery. Methods. Post-operative data were collected from AAA patients from 2 UK Intensive Care Units (ICU). POSSUM and VBHOM based models were compared to the APACHE-AAA model which was able to adjust for the hospital-related effect on outcome. Model performance was assessed using measures of calibration, discrimination and subgroup analysis. Results. 541 patients were studied. The in-hospital mortality rate for elective AAA repair (325 patients) was: 6.2% (95% confidence interval (c.i.) 3.5 to 8.8) and for emergency repair (216 patients) was: 28.7% (95% c.i. 22.5-34.9). The APACHE-based model had the best overall fit to the whole population of AAA patients, and also separately in elective and emergency patients. The V-POSSUM physiology-only (p < 0.001) and VBHOM (p = 0.011) models had a poor fit in elective patients. The RAAA-POSSUM physiology-only (p < 0.001) and VBHOM models (p = 0.010) had a poor fit in emergency patients. Conclusions. The APACHE-AAA model with its ability to adjust for both the hospital-related '' effect '' as well as the patient case-mix, was a more accurate risk stratification model than other contemporary models, in the post-operative AAA patient managed in ICU.