National mental health information priorities 2nd edition

2.6 - Development of casemix for mental health

Page last updated: June 2005

Alongside the work to put routine outcome measures in place, separate research and development was directed to design a casemix classification suited to the needs of the mental health sector. Recognising that the accepted casemix standard (AR-DRG's or Australian Refined National Diagnosis Related Groups) was not appropriate for describing the 'outputs' of mental health services, the National Mental Health Strategy set as one of its priorities the development of an alternative classification model that could be used for both hospital and community-based care.

This subsequently became one of the largest investments on any single project funded over the first five years, with significant implications for future data collections. The Mental Health Classification and Service Costs Project (MH-CASC) was commissioned to determine whether clinical factors explained service costs and whether these could be used to build a patient classification that was both clinically meaningful as well as resource homogeneous. Taking three years to complete, the study collected detailed socio-demographic and service use data on approximately 18,000 consumers attending specialised mental health services, covering 25% of Australia's private and public mental health services.14

The project found that there is an underlying episode classification, not just in inpatient care but also in the community. The volume and type of services (and thus cost) provided to patients was found to have a clinically and statistically logical relationship to the patient's clinical status. The project recommended a first version casemix classification model to be introduced within mental health services that includes 42 patient classes – 19 for community episodes and 23 for inpatient episodes. A summary of the classification is provided in figure 3.

Adoption of the classification requires routine use of a small number of clinical scales, drawn mainly from the same family of instruments used for measuring consumer outcomes and applied at periodic intervals.

National collection and reporting of these data required for the classification began during the Second National Mental Health Plan, in parallel with the introduction of outcome measures. All States and Territories committed under their various Information Development Agreements to pool their data nationally as a resource for the further development of the classification.

Figure 3: Summary of MH-CASC classification

Refer to the following list for a text equivalent of figure 3: Summary of MH-CASC classification
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Text version of figure 3

Summary of MH-CASC classification:
  • All cases - 42 classes

    • Inpatient episodes - 23 classes

      • Ongoing episodes - 12 classes split on age, legal status, diagnosis and HoNOS item (aggression/disruptive behaviour), RUG-ADL

      • Completed episodes

        • Children and adolescents - 3 classes split on diagnosis and HoNOSCA item (disruptive/aggressive behaviour)

        • Adults - 8 classes split on age, diagnosis, legal status, HoNOS total and RUG-ADL

    • Community episodes - 19 classes

      • Children and adolescents - 9 classes split on age, HoNOSCA total, HoNOS item (school problems), CGAS, and psychosocial factors

      • Adults - 10 classes split on focus of care, legal status, HoNOS total and LSP total


14 Buckingham W, Burgess P, Solomon S, Pirkis J and Eagar K (1998). Developing a Casemix Classification for Australia's Mental Health Services. Department of Health and Family Services, Commonwealth of Australia, Canberra.