Define Case Mix Index (CMI) and describe its role in CDI analytics.

• A. CMI is the total number of cases in a hospital per year.
• B. CMI is the average DRG weight of a patient population; higher CMI reflects sicker patient mix and greater resource use, influencing reimbursement and CDI targets.
• C. CMI is the average length of stay of patients, used to measure efficiency.
• D. CMI is the ratio of outpatient to inpatient visits.

Answer: (C)

CMI represents the resource intensity of a hospital’s patient mix, measured as the average DRG weight. In CDI analytics, this is used to understand how complex the typical cases are and how much documentation and coding are needed to accurately reflect severity and comorbidities. A higher CMI means sicker patients and greater expected resource use, which in turn influences reimbursement under DRG-based payment systems and helps set CDI targets to ensure documentation captures the true severity of illness. It’s not about the average length of stay—that's a separate metric used to gauge efficiency. Similarly, CMI isn’t just about the total number of cases or the outpatient/inpatient ratio; those reflect volume or setting, not the mix of case severity and resource use.