Key result
The P-POSSUM mortality prediction algorithm significantly overestimated mortality compared to actual outcomes in surgical ICU patients (21.8% predicted vs 12.2% actual deaths; P<0.001).
Why the study?
Does the P-POSSUM algorithm accurately predict mortality in Australian surgical intensive care unit patients?
Observational (n=229)
No
Does the P-POSSUM algorithm accurately predict mortality in Australian surgical intensive care unit patients?
Effect estimate: AUC 0.68
Absolute Event Rate: 21.8% vs 12.2%
p-value: p=<0.001
The P-POSSUM algorithm over-estimates mortality in Australian surgical intensive care patients and requires further calibration before use as an audit tool.
P-POSSUM use in Australian surgical ICU patients warrants caution; leaves open the need for local recalibration before audit application.
BACKGROUND: The Physiological and Operative Severity Score for enUmeration of Mortality and Morbidity (POSSUM) is an auditing tool designed to compare surgical outcomes independent of case mix. It uses patient physiological and operative data to predict morbidity and mortality for surgical patients. Thus far most evaluations of the POSSUM algorithm and its modifications have emanated from British hospitals. A single-centre retrospective study was therefore performed to determine the applicability of this tool to the Australian surgical case mix. METHODS: All surgical patients undergoing a surgical procedure admitted to the Royal Brisbane Hospital intensive care facility in 1999 were reviewed retrospectively. Mortality predictions using the Portsmouth modification of the POSSUM algorithm (P--POSSUM) were compared to the actual outcomes using receiver-operator characteristic curve analysis and the Hosmer and Lemeshow Goodness-of-Fit test. RESULTS: The records of 229 admissions were reviewed. The area under the receiver-operator characteristic curve was 0.68, significantly greater than 0.5 (P = 0.014). Predicted deaths were significantly greater than actual deaths (50 vs 28, P < 0.001), with over-prediction of death rates in all mortality groupings except the two lowest risk deciles. CONCLUSION: The P-POSSUM algorithm tends to over-estimate mortality in surgical intensive care patients. It may require further calibration before adoption as a surgical audit tool in Australia.
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Organ et al. (2002) conducted an observational in Surgical intensive care unit patients (n=229). P-POSSUM mortality prediction algorithm vs. Actual outcomes was evaluated on Mortality (AUC 0.68, p=<0.001). The P-POSSUM mortality prediction algorithm significantly overestimated mortality compared to actual outcomes in surgical ICU patients (21.8% predicted vs 12.2% actual deaths; P<0.001).
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