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Challenges in comparing risk-adjusted bypass surgery mortality results: results from the Cooperative Cardiovascular
E D Peterson1, E R DeLong, L H Muhlbaier
1The Duke Outcomes Research and Assessment Group, Duke University Medical Center, Durham, North Carolina 27710, USA.
Insights
Comparing bypass surgery mortality risk models showed consistent hospital ratings but varied outlier identification. Risk-adjustment methods impact performance outlier designation, not overall hospital mortality rates.
Area of Science:
- Cardiovascular surgery outcomes research
- Health services research
- Medical informatics
Background:
- Cardiovascular "report cards" commonly use risk-adjusted surgical outcomes for comparisons.
- The impact of different risk-adjustment methods on these comparative metrics is not well understood.
Purpose of the Study:
- To evaluate the predictive accuracy of four clinical risk models for bypass surgery mortality.
- To assess how hospital risk-adjusted surgical outcomes vary based on the applied risk-adjustment method.
Main Methods:
- The Cooperative Cardiovascular Project's Pilot Revascularization Study analyzed 3,654 Medicare patients undergoing bypass surgery at 28 hospitals in Alabama and Iowa.
- Compared the predictive accuracy of four bypass clinical risk models.
- Assessed agreement in hospital-level risk-adjusted outcome performance ratings across different models.
Main Results:
- All four risk models demonstrated similar predictive abilities (C-index: 0.71–0.74), though some overpredicted mortality in high-risk patients.
- High correlation (0.93–0.97) was observed in hospital risk-adjusted mortality rates irrespective of the model used.
- Limited agreement existed in identifying "performance outliers" based on the chosen risk-adjustment model and definition.
Conclusions:
- Hospital risk-adjusted bypass surgery mortality ratings are consistent across different models, supporting their use for provider performance feedback.
- The identification of performance outliers is sensitive to the specific benchmark and methodology employed.
Objectives:
We sought to evaluate the predictive accuracy of four bypass surgery mortality clinical risk models and to examine the extent to which hospitals' risk-adjusted surgical outcomes vary depending on which risk-adjustment method is applied.
Background:
Cardiovascular "report cards" often compare risk-adjusted surgical outcomes; however, it is unclear to what extent the risk-adjustment process itself may affect these metrics.
Methods:
As part of the Cooperative Cardiovascular Project's Pilot Revascularization Study, we compared the predictive accuracy of four bypass clinical risk models among 3,654 Medicare patients undergoing surgery at 28 hospitals in Alabama and Iowa. We also compared the agreement in hospital-level risk-adjusted bypass outcome performance ratings depending on which of the four risk models was applied.
Results:
Although the four risk models had similar discriminatory abilities (C-index, 0.71 to 0.74), certain models tended to overpredict mortality in higher-risk patients. There was high correlation between a hospital's risk-adjusted mortality rates regardless of which of the four models was used (correlation between risk-adjusted rating, 0.93 to 0.97). In contrast, there was limited agreement in which hospitals were identified as "performance outliers" depending on which risk-adjustment model was used and how outlier status was defined.
Conclusions:
A hospital's risk-adjusted bypass surgery mortality rating, relative to its peers, was consistent regardless of the risk-adjustment model applied, supporting their use as a means of provider performance feedback. Designation of performance outliers, however, can vary significantly depending on the benchmark and methods used for this determination.
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