Development of function-related groups version 2.0: a classification system for medical rehabilitation

Area of Science:

• Medical Rehabilitation
• Health Services Research
• Rehabilitation Medicine

Background:

• The Functional Independence Measure-Function Related Group (FIM-FRG) is a case-mix measure used in medical rehabilitation.
• Previous versions required refinement to improve patient classification and predictive accuracy.
• Accurate case-mix classification is essential for effective resource allocation and payment systems in rehabilitation.

Purpose of the Study:

• To introduce and validate Version 2.0 of the FIM-FRG case-mix measure.
• To enhance the classification of patients within medical rehabilitation settings.
• To assess the stability and predictive performance of the new FIM-FRG version.

Main Methods:

• Utilized a large dataset of 85,447 patient discharges from the 1992 Uniform Data System for Medical Rehabilitation.
• Employed recursive partitioning to develop homogeneous groups based on impairment category, admission functional status, and age.
• Validated the system using a separate dataset and evaluated predictive stability with 1990 discharge data.

Main Results:

• FIM-FRG Version 2.0 increased patient classification to 92%, incorporating new impairment categories and an 'evaluation only' group.
• Coexisting medical diagnoses did not significantly improve length of stay (LOS) prediction.
• The system explained 31.7% of the variance in the logarithm of LOS in the validation sample.

Conclusions:

• FIM-FRG Version 2.0 offers more specific impairment categories and higher patient classification rates.
• The measure demonstrates sufficient temporal stability for use in inpatient medical rehabilitation payment systems.
• This enhanced case-mix system provides a robust foundation for reimbursement strategies.