Case-Mix Classification

interRAI assessment systems support the use of algorithms that group individuals into categories reflecting the relative costs of services and supports they are likely to use. These tools are designed to address an enormous challenge faced by governments the world over: how to allocate limited resources in a fair and equitable way. Case mix is by definition a system that classifies  into groups that are homogeneous in their use of resources. A good case-mix system also makes clinical sense, providing meaningful clinical descriptions of individuals in a group. The application of case mix is broad; it provides the basis not only for reimbursement, but also for comparing the populations within/across programs and as a staff planning tool.

Long-Term Care Facilities Case Mix

The best known of the interRAI case-mix systems are the Resource Utilization Groups (RUG-III, RUG-IV) used in institutional long- term care settings. These algorithms provide a person-specific means of allocating health care resources based on the variable costs of caring for individuals with different needs, using specific variables from the interRAI LTCF Assessment instrument (or historically, the MDS 2.0) to create categories of individuals with homogeneous resource use patterns. The RUG-III algorithm explains about 55% of variance in resource use, and it has been validated in a number of countries through a series of international studies.

Home Care

interRAI members have also derived a version of the institutional RUG-III algorithm for use with individuals enrolled in home care called the RUG-III/HC. Version 1.0 RUG-III/HC uses seventy-four variables from the interRAI Home Care instrument to create twenty-three groups with homogeneous resource use patterns. Diagram. The current RUG-III/HC algorithm explains 33.7% of variance in resource use and has been validated in a major Canadian study.

Mental Health

Canadian interRAI members developed a per diem case-mix model, SCIPP, for describing resource use in adult inpatient psychiatric settings, including acute, long stay, forensic, and geriatric psychiatry units. Diagram


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