Utility of the APACHE IV, PPI, and Combined APACHE IV With PPI for Predicting Overall and Disease-Specific ICU and ACU Mortality

Abstract

Background: The Acute Physiology and Chronic Health Evaluation (APACHE) IV and Palliative Performance Index (PPI) are scales commonly used to assess prognosis in intensive care units (ICUs) and acute care units (ACUs). Objective: To compare the utility of APACHE IV, PPI, and combined APACHE IV with PPI for predicting overall and disease-specific mortality. Design: This is a prospective cohort study using admission data during the first 24 hours. Chi-square contingency tables were used to analyze mortality data for each scale. Setting: This study was conducted at a community hospital. Patients: Participants were admitted between December 24, 2008 and April 2, 2010. Results: The APACHE IV, PPI, and APACHE IV plus PPI (n = 599) were significant for predicting overall mortality (P < .0001 each). The APACHE IV was also significant in predicting mortality in patients with congestive heart failure (CHF), pulmonary edema (PULEDEM), stroke (cerebrovascular accident [CVA]), terminal or metastatic cancer (CA), and dementia. The PPI was significant for predicting mortality in PULEDEM, CA, and dementia but not CVA or CHF, while the APACHE IV with PPI was significant for all diseases but CVA. The APACHE IV was the most robust in predicting ICU/ACU mortality. The combined APACHE IV and PPI improved the specificity of the PPI to predict mortality but caused a decline in sensitivity. Limitations: Limitations are due to the subjective nature of the PPI and Glasgow Coma scale (GCS), differences in illness trajectories, and a lack of reliable follow-up of all participants. Conclusion: The benefits of combining scales were best exemplified in participants with dementia. Inconsistencies in the predictive value of specific participant populations are likely due to difference in the illness trajectories of disease processes.