AAA SCORE Developed to Predict Mortality After Open and Endovascular AAA Repair

June 28, 2014—Graeme K. Ambler, MD, et al, in association with the Audit and Quality Improvement Committee of the Vascular Society of Great Britain and Ireland, have developed the Abdominal Aortic Aneurysm Statistically Corrected Operative Risk Evaluation (AAA SCORE) for predicting mortality after open and endovascular interventions to repair abdominal aortic aneurysms (AAAs). Dr. Ambler and colleagues explain the developments and testing of the AAA SCORE in an article published online ahead of print in the Journal of Vascular Surgery (JVS).

These accurate models, which assess the risk of in-hospital mortality after AAA repair, were carefully developed with rigorous statistical methodology and significantly outperform existing methods for both elective cases and overall AAA mortality. These models will be invaluable for both preoperative patient counseling and accurate risk adjustment of published outcome data, concluded the investigators.

The background of this investigation is that accurate adjustment of surgical outcome data for risk is vital in an era of surgeon-level reporting; however, current risk prediction models for AAA repair are suboptimal. Therefore, the investigators aimed to develop a reliable risk model for in-hospital mortality after intervention for AAA, using rigorous contemporary statistical techniques to handle missing data.

As summarized in JVS, the investigators used data collected during a 15-month period in the United Kingdom National Vascular Database. They applied multiple imputation methodology together with stepwise model selection to generate preoperative and perioperative models of in-hospital mortality after AAA repair, using two-thirds of the available data. Model performance was then assessed on the remaining third of the data by receiver operating characteristic curve analysis and compared with existing risk prediction models. Model calibration was assessed by Hosmer-Lemeshow analysis.

The investigators reported that a total of 8,088 AAA repair operations were recorded in the National Vascular Database during the study period, of which 5,870 (72.6%) were elective procedures. Both preoperative and perioperative models showed excellent discrimination, with areas under the receiver operating characteristic curve of .89 and .92, respectively. This was significantly better than any of the existing models (area under the receiver operating characteristic curve for best comparator model, .84 and .88; P < .001 and P = .001, respectively). Discrimination remained excellent when only elective procedures were considered. There was no evidence of miscalibration by Hosmer-Lemeshow analysis, noted the investigators in JVS.