Case Mix Group+ for typical patients

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Text version of infographic

CMG+ — CIHI’s acute care inpatient grouping methodology — aggregates patients into Case Mix Groups (CMGs) with similar clinical and resource utilization characteristics.

80% of all inpatients are typical cases. A typical case is one where a patient received a full course of treatment: they were admitted, treated and discharged. Note that deaths, transfers, long-stay cases and sign-outs are considered atypical; CMG+ indicators are assigned using a different methodology.

How are patients classified into CMG+?

The physician documents clinical information about the patient stay in the medical record. A health care professional identifies

• Diagnosis codes using the ICD-10-CA classification system; and
• When applicable, interventions using the CCI classification system.

Based on the patient’s diagnosis and intervention codes, the admission will be classified into a CMG.

Physician documentation is a key part of the CMG+ methodology.

Diagnoses and interventions that affect the course of treatment are used to assign the Case Mix Group and associated indicators (ELOS and RIW).

How are CMG+ indicators calculated annually?

Expected Length of Stay (ELOS)

• Average days a typical acute inpatient is expected to stay in hospital

Resource Intensity Weight (RIW)

• An estimate of the cost to provide care relative to the average typical inpatient

Base value

The ELOS and RIW base values reflect the average length of stay and the relative cost of cases in the CMG before any adjustments are made. When the patient’s age group is significant, it is used to further refine ELOS and RIW estimates.

Additional factors

The age factor is potentially applicable to every case. There are 4 additional factors that may be applicable to patients based on additional diagnosis or intervention details provided:

• Comorbidity Level (CL): Other diagnosed conditions that significantly increase resource requirements
• Intervention Event (IE): Multiple visits to the operating room in the single admission
• Flagged Intervention (FI): Interventions that are associated with expensive specialized or intensive care
• Out of Hospital (OOH): Specific cardiac interventions that are performed in a different health facility

Final indicator

• ELOS: The average typical length of stay expected for the patient after factor adjustments
• RIW: The average relative resource weight expected for the patient after factor adjustments

How can CMG+ and associated indicators be used?

• Identify hospitals with similar case mixes to make comparisons
• Plan, budget and manage utilization
• Understand and profile your hospital’s patient population
• Support activity-based funding and research

Copyright 2020 Canadian Institute for Health Information

How to cite this document: Canadian Institute for Health Information. Case Mix Group+ for typical patients [infographic]. Ottawa, ON: CIHI; 2020.