Case Mix Index (CMI)
What is case mix index (CMI)?
Case mix index is a metric that reflects the diversity, complexity, and severity of the patients treated at a healthcare facility, such as a hospital. Case mix index is used by the Centers for Medicare and Medicaid Services (CMS) to determine hospital reimbursement rates for Medicare and Medicaid beneficiaries.
How do you calculate case mix?
Case mix index is calculated by adding up the relative Medicare Severity Diagnosis Related Group (MS-DRG) weight for each discharge, and dividing that by the total number of Medicare and Medicaid discharges in a given month and year.
Why is case mix index an important healthcare metric?
Higher case mix index values indicate that a hospital has treated a greater number of complex, resource-intensive patients, and the hospital may be reimbursed at a higher rate for those cases.
Companies that sell into healthcare facilities can also use the metric to target and segment accounts. Hospitals with the highest case mix index tend to be specialty and surgical hospitals that perform complex and high-cost procedures.
What factors influence case mix index?
Many factors can influence case mix index, including but not limited to:
- Coding accuracy
- Documentation specificity
- Patient comorbidities
- Patient population
- High volumes of highly weighted DRGs (like organ transplantations, cardiothoracic surgeries, or neurosurgeries)
- Annual updates to relative MS-DRG weights
