Case Mix Index (CMI) is used by the Centers for Medicare and Medicaid Services (CMS) to determine funding allocation for Medicare and Medicaid beneficiaries in hospitals and other care facilities. Patients are classified into diagnosis-related groups (DRGs) depending on condition, case complexity, and medical needs. CMS is able to evaluate the resources required to treat patients in each DRG compared to other DRGs and to patients outside a DRG.
Case mix is used to find and adjust the average care cost per patient at a hospital or other care facility based on the patient population demographics. This can have an impact on quality ratings and reimbursement rates, as the weight of each DRG is determined by CMS.
Hospital case mix index calculation
As an example, if a hospital’s average cost per patient is $1,000 and its annual CMI is 0.80, the adjusted cost per patient would be $1,250. CMI is a vital indicator of hospital performance because of the way it impacts finances.
The following tables list the top 25 hospitals with the largest case mix index. The average CMI of all 25 hospitals is 3.48, though CMIs range from 3.02 to 5.26. This is a shift up from the last reporting period, which ranged from 2.75 to 4.88. CMI does not appear to correlate to the number of annual discharges, with discharges from the top 10 hospitals ranging from 5,531 to 87 annually.
Many of the hospitals with the highest CMI are located in Indiana (12 percent), Louisiana (16 percent), and Texas (32 percent). This is a shift from the previous reporting year, in which the hospitals with the highest CMI were in in Louisiana (14 percent), Oklahoma (12 percent), and Texas (28 percent).
The concentration of high CMI is likely due to barriers to care access in rural parts of these states, and high concentrations of patients with chronic illnesses that require patients to seek insurance through Medicare and Medicaid.