Comparison of three contemporary risk scores for mortality following elective abdominal aortic aneurysm repair.
OBJECTIVE
A number of contemporary risk prediction models for mortality following elective abdominal aortic aneurysm (AAA) repair have been developed. Before a model is used either in clinical practice or to risk-adjust surgical outcome data it is important that its performance is assessed in external validation studies.


METHODS
The British Aneurysm Repair (BAR) score, Medicare, and Vascular Governance North West (VGNW) models were validated using an independent prospectively collected sample of multicentre clinical audit data. Consecutive, data on 1,124 patients undergoing elective AAA repair at 17 hospitals in the north-west of England and Wales between April 2011 and March 2013 were analysed. The outcome measure was in-hospital mortality. Model calibration (observed to expected ratio with chi-square test, calibration plots, calibration intercept and slope) and discrimination (area under receiver operating characteristic curve [AUC]) were assessed in the overall cohort and procedural subgroups.


RESULTS
The mean age of the population was 74.4 years (SD 7.7); 193 (17.2%) patients were women and the majority of patients (759, 67.5%) underwent endovascular aneurysm repair. All three models demonstrated good calibration in the overall cohort and procedural subgroups. Overall discrimination was excellent for the BAR score (AUC 0.83, 95% confidence interval [CI] 0.76-0.89), and acceptable for the Medicare and VGNW models, with AUCs of 0.78 (95% CI 0.70-0.86) and 0.75 (95% CI 0.65-0.84) respectively. Only the BAR score demonstrated good discrimination in procedural subgroups.


CONCLUSIONS
All three models demonstrated good calibration and discrimination for the prediction of in-hospital mortality following elective AAA repair and are potentially useful. The BAR score has a number of advantages, which include being developed on the most contemporaneous data, excellent overall discrimination, and good performance in procedural subgroups. Regular model validations and recalibration will be essential.
The University of Manchester, Manchester Academic Health Science Centre, UHSM, Academic Surgery Unit, Education and Research Centre, Manchester, UK; University College London, National Institute for Cardiovascular Outcomes Research, Institute of Cardiovascular Science, London, UK. Electronic address: stuart.grant@manchester.ac.uk.
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Grant
University College London, National Institute for Cardiovascular Outcomes Research, Institute of Cardiovascular Science, London, UK; The University of Manchester, Manchester Academic Health Science Centre, Centre for Health Informatics, Manchester, UK.
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Hickey
The University of Manchester, Manchester Academic Health Science Centre, UHSM, Academic Surgery Unit, Education and Research Centre, Manchester, UK.
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Carlson
The University of Manchester, Manchester Academic Health Science Centre, UHSM, Academic Surgery Unit, Education and Research Centre, Manchester, UK.
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McCollum
D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000175:diagnosis / Q000401:mortality / Q000601:surgery*; D019540:Area Under Curve; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000401:mortality*; D016009:Chi-Square Distribution; D003661:Decision Support Techniques; D016002:Discriminant Analysis; D017558:Elective Surgical Procedures; D057510:Endovascular Procedures / Q000009:adverse effects / Q000401:mortality*; D004739:England / Q000453:epidemiology; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D008297:Male; D008485:Medical Audit; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D016896:Treatment Outcome
Abdominal aortic aneurysm; Clinical prediction rule; In-hospital mortality; Risk adjustment