Revisiting the validity of APACHE II in the trauma ICU: improved risk stratification in critically injured adults

Abstract

Background: Quality and benchmarking initiatives highlight the need for accurate stratified risk adjustment. The stratification of trauma patients has relied on scores specific to trauma populations. While the Acute Physiologic and Chronic Health Evaluation (APACHE) II score has been considered "invalid" in the trauma population, we hypothesized that APAHCE II would more accurately predict outcomes in critically injured patients in whom commonly used trauma scores have inherent limitations.

Methods: A prospective cohort of critically injured patients was enrolled. Severity scores and their sub-components were collected, and in-hospital mortality was assessed. The area under the receiver operating characteristic (AUROC) curve was used to determine the predictive value of each score. Logistic regression estimated the odds of death associated with incremental changes in severity scores and their subcomponents.

Results: 1019 patients were available for analysis. APACHE II was the best predictor of mortality (AUROC 0.77 versus AUROC 0.54 for ISS and 0.64 for TRISS). A unit increase in APACHE II was associated with an OR of death of 1.18 (95% CI 1.14-1.22). The components of APACHE II that contributed the most to its accuracy included temperature, serum creatinine and the Glasgow Coma Scale (GCS).

Conclusion: Critically injured patients have physiologic derangements not accurately accounted for by commonly used trauma scores. In this subset a more general ICU scoring system is useful for risk adjustment for research, administrative and quality improvement purposes.

Trial registration: ClinicalTrials.gov NCT00170560.

Figure 1

Receiver Operating Characteristic Curves for ISS, TRISS and APACHE II for predicting in-hospital mortality in a subset of critically ill trauma patients.