The Canadian Institute for Health Information (CIHI) is adapting the Comprehensive Ambulatory Classification System (CACS) to group Level 2 emergency department (ED) data submitted to the National Ambulatory Care Reporting System (NACRS). (Currently only Level 3 ED data is grouped.) CACS for NACRS Level 2 will be available in April 2018.


CIHI plays a critical role in the development of Canada’s health information system. Grouping methodologies such as Case Mix Group+ (CMG+) and CACS are de facto standards for grouping hospital patients with similar treatment requirements in Canada. Over the years, health care facilities have applied these methodologies and accompanying resource indicators to effectively plan, monitor and manage the services they provide.

The CACS methodology groups many types of ambulatory care data submitted to NACRS, including day surgery, rehabilitation and medical clinic, and ED data. Currently, CIHI processes and groups only Level 3 submissions, which include a number of clinical and demographic data elements, in addition to diagnoses and interventions.


When NACRS first launched in 1997, there was only 1 level of submission. To address clients’ need to reduce the burden of data collection and to improve the timeliness of reporting, CIHI implemented levels of NACRS ED data submission as follows:

  • NACRS ED Level 1, introduced in 2009–2010, requires data elements to be used in the calculation of ED wait time indicators — data elements such as Time of Registration, Triage Time, Disposition Time and CTAS Level. These data elements are often readily available from hospital admission/discharge and/or ED information systems and can be interfaced to the NACRS abstract.
  • Reporting Level 2 became available in 2010–2011. It includes the same mandatory and optional elements as Level 1, but completion of clinical information selected from pick-lists — either the ED Discharge Diagnosis Short List or the Presenting Complaint List — is required.
  • Level 3 data (the original version of NACRS) is currently the only level that is grouped in the CACS methodology. In 2011, CIHI released a redeveloped version of CACS, which included a separate logic step to group ED visits into their own clinically relevant cells. A client request to run NACRS Level 2 data through the CACS grouping methodology initiated a project to assess the value and usability of the cells and resource indicators, to document issues and to offer solutions.

ED discharge diagnosis

Although Level 2 NACRS includes clinical data elements, only the ED discharge diagnosis will be used for case-mix assignment. The ED discharge diagnosis is a subset of the diagnosis codes available for the Main Problem data element, which is used for grouping Level 3 abstracts.

Intervention pick-list

Level 1 and Level 2 NACRS submissions were developed to reduce the burden of data collection and to improve the timeliness of reporting. It became apparent though, after analysis, that if resource indicators were to become a CIHI output for Level 2, along with diagnostic information, the capture of interventions performed in the ED would be necessary to create representative weights.

Work is currently under way to modify the NACRS record for April 2018. Data elements will be added to capture 3 occurrences of interventions (from a pick-list of 28) that have shown to increase the resource intensity of a client visit. Investigative technology, or IT (CT scan, X-ray, etc.), also plays a role in describing the cost of an ED visit. Data elements to capture 3 occurrences of IT (from a pick-list of 9) will also be added.
Details regarding the modifications to NACRS are available in the CAD bulletins.

Stay tuned for more information in September 2017!