The Comprehensive Ambulatory Classification System (CACS) is a grouping methodology designed to group ambulatory patient data for emergency department, day surgery and clinic visits. The CACS methodology is based on ICD-10-CA and CCI codes and a few other data elements to categorize patients into statistically and clinically homogeneous groups.
Overview of the methodology
CACS groups ambulatory patient data:
- Emergency, day surgery and outpatient clinic data from the National Ambulatory Care Reporting System (NACRS)
- Day surgery visit data from the Discharge Abstract Database (DAD)
This grouping methodology uses ICD-10-CA and CCI codes and selected NACRS or DAD data elements to classify ambulatory patients. It also estimates a Resource Intensity Weight (RIW) for each patient visit. The CACS RIW methodology is included in the CACS Directory. Additionally, Ontario-specific CACS RIW values are assigned to that jurisdiction’s records.
Accessing the methodology
The CACS Directory is a detailed reference manual that includes a logic overview, a comprehensive set of flowcharts, and a list of CACS groups and associated base RIWs.
The most recent CACS directories are available through CIHI’s eStore
CACS client tables provide common case-mix information in tab-delimited ASCII format that can be used for analysis. CACS client tables include the following:
- Descriptions of major ambulatory cluster (MAC), CACS and Investigative Technology categories, which can be linked to data grouped with the associated CACS methodology year
- CCI and ICD-10-CA code finders, which can be used to identify the possible CACS cell assignment for each code (including NACRS Level 3 submissions and NACRS Level 2 pick-list codes)
- CACS RIW tables used for Base RIW, Investigative Technology Overlay and Interaction Assignment, which allow for a better understanding of how the CACS RIW is calculated
- Functional Area CACS RIW proportion tables, which can be used in combination with the RIWs to estimate resource use per functional area for each CACS cell
The most recent CACS tables are available through CIHI’s eStore:
Methodology in action
Annually, when a new version of the CACS methodology is released, the most recent 5 years of data are regrouped and provided to stakeholders to allow for trending in a common methodology year.
Client visit data collected in NACRS and grouped by CACS can be used to support
- Management decision-making at the facility level
- Resource allocation decisions at global and facility levels
- Provincial and national comparisons
- The effective analysis of ambulatory care services
Ambulatory care volumes by CACS as well as CACS RIW/cost estimate reports can be found in Your Health System: Insight (login required).
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