Short Info: CMG (Canada)

In Canada, a first CMG system was introduced as early as 1983. It was inspired by the HCFA-DRG system.1

There are some peculiarities concerning terminology here. Instead of "Major Diagnostic Categories" (MDCs), "Major Clinical Categories" (MCCs) were used. And instead of the principal diagnosis, the CMG-grouping used the "Most Responsible Diagnosis" (MRDx) as its starting point. (The concept points out the "most important" diagnosis, that is, the one with greatest influence on the length of stay.)

In 1997, the system was restructured. All age and CC-splits were eliminated. Instead, four "Complexity Levels" and three age levels were defined. The revised system was then renamed "Case Mix Groups with Complexity Overlay and Age Adjustement" (CMG/Plx). It carried 477 CMGs, encompassing 3413 refined "APLX groups".2

In 2007, a further fundamental recast followed.3 The number of main categories was reduced from 25 to 21. CC lists were defined for each main category. A total of 558 base CMGs were defined.

The base CMGs could now be split, according to needs, by using up to five pre-defined "factors":

• Age categories (9 levels).
• Co-morbidity driven severity categories (5 levels).
• Flagged interventions (lists for 14 categories of interventional procedures).
• Number of interventions (3 categories).
• Interventions carried out outside the hospital (list).