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POSSUM and P-POSSUM overpredict mortality for carotid endarterectomy
G Kuhan1, A F Abidia, L D Wijesinghe
1Academic Vascular Unit, Hull Royal Infirmary, Hull, UK.
Insights
The Physiological and Operative Severity Score for the enUmerged Surgical Mortality (POSSUM) and its Portsmouth modification (P-POSSUM) overpredict mortality for Carotid Endarterectomy (CEA) patients. These models are unsuitable for audit, suggesting a need for CEA-specific prediction tools.
Area of Science:
- Vascular Surgery
- Surgical Outcomes Research
- Health Services Research
Background:
- Carotid Endarterectomy (CEA) is a common procedure to prevent stroke.
- Accurate mortality prediction is crucial for surgical audit and patient risk stratification.
- Existing scoring systems like POSSUM and P-POSSUM are widely used but their applicability to specific procedures like CEA requires validation.
Purpose of the Study:
- To evaluate the predictive accuracy of the POSSUM and P-POSSUM scoring systems for 30-day mortality in patients undergoing CEA.
- To determine if these general surgical risk models are suitable for comparative audits of CEA procedures.
Main Methods:
- A retrospective and prospective study involving 499 CEAs performed between 1992 and 1999.
- Collection of patient physiological and operative parameters, and 30-day mortality data.
- Calculation of predicted mortality using POSSUM and P-POSSUM, followed by chi-squared analysis to compare observed versus predicted deaths.
Main Results:
- The observed 30-day mortality rate was 1.8% (9 out of 499 patients).
- POSSUM and P-POSSUM predicted significantly higher mortality rates (49 and 25, respectively) compared to the observed nine deaths.
- Statistical analysis revealed a significant lack of fit for both models (p<0.05), indicating poor predictive accuracy.
Conclusions:
- Both POSSUM and P-POSSUM demonstrate a tendency to overpredict mortality in patients undergoing CEA.
- These models are not suitable for comparative audit purposes in the context of CEA.
- Development of specific risk prediction models tailored for CEA procedures is recommended for improved accuracy.
Objectives:
the aim was to test the predictive accuracy of POSSUM and P-POSSUM on patients undergoing CEA.
Design:
retrospective and prospective study.
Materials:
499 CEAs performed by four vascular surgeons from a single unit from 1992-99. The median age was 68 (range 38-86) and 60% were men.
Methods:
physiological parameters, operative parameters and the 30-day mortality were collected. Predicted mortality for each patient was calculated using POSSUM and P-POSSUM equations. Patients were stratified into risk groups and observed and predicted deaths were compared. Accuracy of the prediction was assessed using chi-squared analysis.
Results:
the observed 30-day mortality was 1.8% (9/499). The predicted deaths using POSSUM and P-POSSUM analysis were 49 and 25 respectively compared to nine observed deaths. There was significant evidence of lack of fit of both models in predicting mortality (chi-squared analysis, p<0.05).
Conclusions:
POSSUM and P-POSSUM overpredict mortality and are unsuitable for comparative audit of CEA. Models developed specific for CEA might accurately predict mortality.
