Postpandemic Recovery of Case Mix Index and Risk-Adjusted Mortality in US Hospitals

Area of Science:

• Healthcare quality research
• Epidemiology
• Health services research

Background:

• The COVID-19 pandemic significantly impacted hospital quality and patient safety metrics.
• There is a need to understand if established trends in hospital outcomes have resumed post-pandemic.

Purpose of the Study:

• To evaluate if risk-adjusted mortality and case mix index (CMI) trends among hospitalized patients have returned to their pre-pandemic trajectories.
• To analyze changes in hospital quality indicators following the COVID-19 pandemic.

Main Methods:

• Retrospective cohort study utilizing the Vizient Clinical Data Base (over 1300 US hospitals).
• Analysis of inpatient discharges from October 2019 to March 2024.
• Employed ordinary least squares (OLS) and joinpoint regression to assess trends and identify inflection points in CMI and standardized mortality ratio (SMR).

Main Results:

• Mean CMI increased from 1.70 (Q4 2019) to 1.79 (Q1 2024), with no significant overall linear trend but an inflection point in Q4 2020.
• Mean standardized mortality ratio (SMR) decreased from 1.00 (Q4 2019) to 0.80 (Q1 2024), showing a significant linear decline across the study period.
• An SMR inflection point was identified in Q3 2021, after which SMR declined significantly by -3.17% per quarter.

Conclusions:

• Risk-adjusted in-hospital mortality has significantly declined post-pandemic, resuming its prepandemic improvement trajectory.
• Patient acuity, as indicated by CMI, has remained elevated, suggesting a new postpandemic baseline.
• Hospital mortality outcomes have returned to prior improvement trends, despite increased patient acuity.