Director's Note: Use case-mix index metrics with caution

Many CDI managers use case-mix index (CMI) as the primary metric for determining the success or failure of their program. If the CMI rises in a given month, the CDI staff is doing its job, appropriately querying physicians for the correct principal diagnosis and accompanying complications/comorbidities.

If the CMI dips, CDI staff aren’t getting physicians to respond, or aren’t reviewing records thoroughly enough. Or so goes the common logic. But using CMI as your solitary or even principal metric for success is fraught with problems. Sure, CMI shows a good snapshot of the type of patients a hospital is treating. But as a cold piece of data in isolation it does not tell the story of what is going on inside the walls of a given facility.