The Case Mix Index (CMI) represents the average relative weight of a hospital’s cases. It is calculated by summing the Diagnosis Related Group (DRG) weights for all patients discharged during a specific period, and then dividing by the total number of discharges. For example, if a hospital discharged 100 patients, and the sum of the DRG weights for those patients was 125, the CMI would be 1.25.
This metric offers valuable insights into the complexity and resource intensity of the patient population served. A higher CMI generally indicates that a hospital is treating a more complex and resource-intensive mix of patients. Understanding this figure is crucial for financial planning, resource allocation, and performance benchmarking. Its evolution has been driven by the need for standardized measures reflecting hospital output beyond simple volume metrics.