Concept: Case Mix Groups (CMGs™) versus Diagnosis Related Groups (DRGs™)
Last Updated: 2001-03-22
1. Case Mix:
- group cases into manageable number of meaningful patient categories
- patients within each category are similar clinically and in terms of resource use
- use administrative data to group cases
- algorithm of DRG™/CMG™ assignments is identical except that CMGs™ were designed to be grouped according to the most responsible diagnosis
- within each category cases separated into medical and surgical.
- then CMG™/DRG™ assigned.
RIWs™: Resource Intensity Weights are the weights associated with CMGs™. They are based on charge data from Maryland and Canadian LOS
- Available from CIHI with CMG™ grouper
- DRG™ weights: weights associated with DRGs™ based on Medicare patients only; available from the USA
RDRGs® - for DRGs™
Complexity overlay - for CMGs™
These two refinements are very similar - CMGs™ also have age adjustment factor.
Weights available for complexity/intensity refinement:
- RDRG® weights developed at MCHP for RDRGs®.
- RIWs™ for complexity overlay.
Both are patient classification systems that provide ways of describing the types of patients a hospital treats (its case mix).
Diagnoses 01 to 25: mutually exclusive categories based on body systems.
Both CMGs™ and DRGs™ have weights associated with them that are supposed to reflect the relative costs for each group.
3. Complexity / Intensity of Refinement:
- Unlike DRGs™, CMGs™ may change number from one year to the next. This can create problems for longitudinal studies.
- With CMG™ - they use diagnosis typing - can distinguish between a comorbidity (pre-existing additional diagnosis) and a complication (diagnosis that arose after admission). (DRG™ - comorbidities and complications are grouped together).
- DPGs - (Day Procedure Groups) outpatient grouper and weights are available from CIHI. For more information, please see the CIHI Web Site at: https://www.cihi.ca/en/data-and-standards/standards/case-mix/day-procedure-groups-dpg .
2. Complications and Comorbidities:
- Case Mix Groups (CMG™) - Overview
- Diagnosis Related Groups (DRGs™) - Overview
- Hospital Care Cost Index
- Health Measures
Manitoba Centre for Health Policy
Community Health Sciences, Max Rady College of Medicine,
Rady Faculty of Health Sciences,
Room 408-727 McDermot Ave.
University of Manitoba
Winnipeg, MB R3E 3P5 Canada