The Case Mix department is on a 3-year cycle for methodology changes. On April 1, 2018, we'll release a new version of the Comprehensive Ambulatory Classification System (CACS). We've added new ICD-10-CA/CCI codes and also made a number of changes to the logic steps in the classification.

Emergency department

Beginning April 1, 2018, the CACS grouping methodology will group both NACRSi Level 2 and Level 3 data. To ensure comparability, the data element ED Discharge Diagnosis will be used to group Level 2 records instead of the Main Problem, which is used to group Level 3 records. To account for the variation in resource consumption associated with interventions in a Level 3 abstract, a pick-list of interventions has been added to Level 2 data submissions.

NACRS data elements used in CACS ED logic

NACRS Level 3

  • ED Visit Indicator (139)
  • Main Problem (44)
  • Interventions (46/47a–i)

  • Anaesthetic Technique (53)
  • Birth Date (08)
  • Visit Disposition (35)

NACRS Level 2

  • ED Visit Indicator (139)
  • ED Discharge Diagnosis (137)
  • NEW
    • ED Intervention Pick-List (173a–c)
    • ED Investigative Technology Pick-List (174a–c)
    • Number of ED IT Performed (175a–c)
  • Anaesthetic Technique (53)
  • Birth Date (08)
  • Visit Disposition (35)

New look for the emergency department

We've changed the flow of the intervention-driven ED cells in order to add clinical meaning, ensure volume and reflect variation in resource consumption. High-resource interventions will be grouped in the first step of the ED logic, followed by those visits that end in admission. Diagnosis will be used to assign the remaining visits, with additional splits on the presence of moderate or minor resource interventions, where volume and/or cost allow.

Details will be outlined in the CACS Directory 2018.

Rehabilitation clinics and medical clinics

Rehabilitation clinics defined by Program Area (NACRS data element 98) will now include a second split when the Mode of Visit (NACRS data element 20) is 2 — Visit (face-to-face) with a group of patients at facility where appropriate.


  • D101 Recreational Therapy
  • D105 Recreational Therapy, Group Session

3 medical clinics will also split on Mode of Visit:

  • E211 Cardiovascular Disorders, Group Session
  • E711 Mental Health Disorders, Group Session
  • E762 Other Medical and Follow-up Care, Group Session

Intervention-driven cells

New CCI codes will be added to the existing CACS cells. Some modifications are being made to the intervention-driven cells where costs or volume warrant. For example, skin interventions will no longer be split by anatomy. The new cells are shown below:


  • C353 Abdomen and Trunk Skin Intervention
  • C354 Face and Neck Intervention
  • C355 Other Skin Intervention


  • C357 Tissue Expander and Other Special Skin Intervention
  • C358 Major Skin Intervention
  • C359 Minor Skin Intervention

Details of the changes will be highlighted in the web conference What's New for Case Mix Acute Care, 2018, coming in March 2018.


i. National Ambulatory Care Reporting System