How is CMI calculated?

• A. Total Weighted Volume / Number of patients
• B. Total Weighted Volume x Number of patients
• C. Sum of Relative Weights
• D. Total Weighted Volume / Number of patients

Answer: (D)

CMI reflects the average complexity or resource use per patient. It’s calculated by taking the total weighted volume (the sum of DRG relative weights for all patients) and dividing by the number of patients. This division produces the average weight per patient, which is the CMI.

For example, if three patients have DRG weights 1.2, 2.0, and 0.8, the total weighted volume is 4.0. Dividing by 3 patients gives a CMI of 1.33. Using just the sum of weights would not give an average, and multiplying by the number of patients would overstate the measure.