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Adjusting outcome measurements for case-mix in a vascular surgical register--is it possible and desirable?
J Elfström1, T Troëng, A Stubberöd
1Department of Vascular Surgery, University Hospital, Linköping, Sweden.
Insights
Infrainguinal bypass surgery outcomes varied significantly between departments, influenced by patient factors and surgical choices. Adjusting for case-mix revealed that distal anastomosis location was key to explaining patency rate differences.
Area of Science:
- Vascular Surgery
- Clinical Audit
- Surgical Outcomes Research
Background:
- Infrainguinal bypass surgery is a critical procedure for limb salvage.
- Variations in surgical outcomes between institutions can impact patient care.
- Understanding case-mix influence is essential for accurate performance evaluation.
Purpose of the Study:
- To analyze variations in infrainguinal bypass surgery outcomes across different surgical departments.
- To determine if case-mix differences influenced observed outcome variations.
- To identify factors contributing to outcome disparities.
Main Methods:
- Retrospective analysis of 764 infrainguinal bypass operations (1988-1990).
- Data collected from six Swedish surgical departments.
- Outcomes assessed at 30 days and 1 year, including mortality, amputation, and patency rates.
Main Results:
- Significant variations (p < 0.01) observed in mortality, amputation, and 30-day patency rates.
- Case-mix differences noted in indication, distal anastomosis location, and graft type.
- Regression analysis identified age, diabetes, heart disease, anastomosis location, and graft type as significant factors; hospital also emerged as significant.
Conclusions:
- Location of the distal anastomosis was the primary factor in adjusting for case-mix when evaluating bypass graft patency.
- Departmental variations in outcomes are influenced by both patient case-mix and surgical practice.
Objective:
We analysed the variation in the outcome of infrainguinal bypass surgery between departments in a register for clinical audit to see if variation in case-mix influenced the results.
Materials And Methods:
The study was a retrospective analysis of 764 infrainguinal bypass operations performed from 1988 to 1990 at six Swedish surgical departments. Results were assessed at 30 days and at 1 year postoperatively.
Results:
There was a significant variation (p < 0.01) in mortality and amputation rates both at 30 days and at 1 year and in patency rate at 30 days. There were also differences in case-mix. Differences were found in indication, location of distal anastomosis and graft type. Regression analysis found that mortality was influenced by age, diabetes and heart disease and patency rate by location of the distal anastomosis and graft type. When 'hospital' was added as a variable in the regression analysis it was also found to be a significant indicator.
Conclusion:
Location of the distal anastomosis was the main factor in adjusting patency for case-mix.