What is the Case-Mix Index (CMI)?
The case-mix index (CMI) in healthcare is a metric that reflects the diversity and complexity of the patients treated in a particular medical facility.
It is calculated based on the relative value assigned to each patient's Diagnosis-Related Group (DRG). A higher CMI indicates that a healthcare facility treats patients with more complex or severe medical conditions, often requiring more resources and intensive care.
The CMI is crucial for determining hospital reimbursement rates, as it influences the amount of funding a facility receives for patient care.
Calculation of the case-mix index?
The case-mix index (CMI) is calculated by taking the average of the relative weights of all Diagnosis-Related Groups (DRGs) for patients treated in a healthcare facility over a specific period. Here's a step-by-step overview of how it is calculated:
- Each patient's diagnosis is categorized into a Diagnosis-Related Group (DRG), which has a specific relative weight assigned based on the complexity and resource intensity of the treatment required.
- Add the relative weights of all DRGs for the patients treated during the period.
- Determine the total number of cases(patients) treated during the same period.
- Divide the total sum of the DRG weights by the total number of cases to get the CMI.
CMI=Sum of DRG Weights/Total Number of Cases
This average represents the facility's CMI, which indicates the overall complexity of the patient population's case mix. A higher CMI means the facility deals with more complex cases, typically requiring more resources.
Example of case mix index (CMI)
Tertiary care hospital
Suppose there is a large urban tertiary care hospital; the medical team is preparing for a busy week in the cardiac unit. They've admitted several patients with severe and complex conditions that require intensive care and advanced surgical procedures.
Each patient is assigned a Diagnosis-Related Group (DRG) with a specific relative weight. For
instance, there are five patients with different DRG weights, such as:
Patient 1: DRG Weight = 4.2 (Heart surgery)
Patient 2: DRG Weight = 3.8 (Oncology treatment)
Patient 3: DRG Weight = 2.5 (Complex neurological procedure)
Patient 4: DRG Weight = 1.1 (Routine procedure)
Patient 5: DRG Weight = 1.6 (Moderate complexity case)
Calculation of CMI:
Total DRG Weight = 4.2 + 3.8 + 2.5 + 1.1 + 1.6 = 13.2
Number of Cases = 5
CMI = 13.2 / 5 = 2.64
With a CMI of 2.64, this hospital's case mix reflects the high complexity and intensity of care required for its patients. This higher CMI suggests that the hospital is managing a significant number of resource-intensive cases, which influences the level of care and the hospital's reimbursement rates.