Establishing score equivalence of the Functional Independence Measure motor scale and the Barthel Index, utilising the International Classification of Functioning, Disability and Health and Rasch measurement theory
Birgit Prodinger, Rory J. O’Connor, Gerold Stucki, Alan Tennant
ICF Unit, Swiss Paraplegic Research (SPF), Guido A. Zäch Institute, CH-6207 Nottwil, Switzerland. E-mail: firstname.lastname@example.org
Introduction: Two widely used outcome measures to assess functioning in neurological rehabilitation are the Functional Independence Measure (FIM™) and the Barthel Index. The current study aims to establish the equivalence of the total score of the FIM™ motor scale and the Barthel Index through the application of the International Classification of Functioning, Disability and Health, and Rasch measurement theory.
Methods: Secondary analysis of a large sample of patients with stroke, spinal cord injury, and multiple sclerosis, undergoing rehabilitation was conducted. All patients were assessed at the same time on both the FIM™ and the Barthel Index. The International Classification of Functioning, Disability and Health Linking Rules were used to establish conceptual coherency between the 2 scales, and the Rasch measurement model to establish an exchange of the total scores.
Results: Using the FIM™ motor scale, items from both scales linked to the International Classification of Functioning, Disability and Health d4 Mobility or d5 Self-care chapters. Their co-calibration satisfied the assumptions of the Rasch model for each of 3 diagnostic groups. A ceiling effect was observed for the Barthel Index when contrasted against the FIM™ motor scale.
Conclusion: Having a Rasch interval metric to transform scores between the FIM™ motor scale and Barthel Index is valuable for monitoring functioning, meta-analysis, quality audits and hospital benchmarking.
Improving functioning, which includes aspects of self-care and mobility, is the main aim of rehabilitation. To be able to measure changes in functioning, the Functional Independence Measure (FIM™) motor scale and the Barthel Index are the most commonly used tools in rehabilitation. However, if one clinic uses the FIMTM and another clinic the Barthel Index, the performance of the clinics with regards to improving functioning cannot be directly compared. Thus, we developed in this study a transformation table that allows exchanging scores between the Functional Independence Measure (FIM™) motor scale and the Barthel Index for people undergoing rehabilitation due to stroke, spinal cord injury and multiple sclerosis.
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