102: DOES CASE MIX INDEX TELL THE STORY OF HOW SICK OUR PATIENTS ARE IN AN ICU?

Abstract

Introduction: CMS uses the case mix index for calculating payments, not for disease severity per se. It is variable based on documentation and coding. APACHE and Acute physiological scoring (APS) are developed to predict disease severity and mortality in ICU. Houston Methodist Baytown (HMB) is considered a complex care hospital for Vizient. The billing and compliance department reviews our ICU documentation periodically. Higher ICU-related DRG services like tracheostomy, ECMO, impella are done. We wanted to evaluate if CMI correlates with mortality rate compared to APACHE and APS in a complex care hospital. Methods: Retrospective study of ICU data at HMB, a 24-bed medical-surgical ICU from Jan 2021 to March 2022. CMI, APACHE, and APS were obtained from ICU (clarity database, EPIC) and VICU dashboards. Descriptive statistics and Pearson correlation was used to evaluate CMI and APACHE, APS in predicting mortality rate. The mortality rate is defined as a percentage of patients with ICU stays who expired during an ICU stay. The mortality index is defined as the observed mortality rate/ expected mortality rate. Results: We had 2758 ICU encounters from January 2021 to March 2022. Mean CMI- 3.426, Mean APACHE -65, Mean APS -54. The average Mortality rate is 8.8%, average mortality index is 0.61. There is a strong positive correlation between APACHE- r=0.914, p=0.029; APS- r= 0.947, p= 0.014 and mortality. CMI also correlated well with mortality r=0.9131, p=0.03. Conclusions: APACHE and APS have strong correlations to predict mortality however CMI also correlated well with the mortality rate for complex care ICU patients. If appropriate documentation and high-risk patient services are provided, then CMI in those hospitals might correlate well with the ICU mortality rate.