A Rasch-Based Comparison of the Functional Independence Measure and Spinal Cord Independence Measure for Outcome and Quality in the Rehabilitation of Persons with Spinal Cord Injury

Abstract

Objective: The Functional Independence Measure (FIM™) and spinal cord injury (SCI)-specific Spinal Cord Independence Measure (SCIM) are commonly used tools for outcome measurement and quality reporting in rehabilitation. The objective of this study was to investigate the psychometric properties of FIM™ and SCIM and to equate the 2 scales. Methods: First, content equivalence of FIM™ and SCIM was established through qualitative linking with the International Classification for Functioning, Disability and Health (ICF). Secondly, a Rasch analysis of overlapping contents determined the metric properties of the scales and provided the empirical basis for scale equating. Furthermore, a transformation table for FIM™ and SCIM was created and evaluated. Subjects: Patients with SCI in Swiss inpatient rehabilitation in 2017–18. Results: The ICF linking and a separate Rasch analysis of FIM™ restricted the analysis to the motor scales of FIM™ and SCIM. The Rasch analysis of these scales showed good metric properties. The co-calibration of FIM™ and SCIM motor scores was supported with good fit to the Rasch model. The operational range of SCIM is larger than for FIM™ motor scale. Discussion: This study supports the advantage of using SCIM compared with FIM™ for assessing the functional independence of patients with SCI in rehabilitation. LAY ABSTRACT In our study we compared two rehabilitation outcome assessment tools commonly used to measure functional independence in Spinal Cord Injury: the Functional Independence Measure (FIM™), a general tool, and the Spinal Cord Independence Measure (SCIM), a tool specifically developed for Spinal Cord Injury rehabilitation. We first compared the content of the two tools using the International Classification of Functioning Disability and Health (ICF). Then we tested their measurement properties and put them on a common measurement scale, which allows to directly compare scores of the two tools. The common measurement scale was obtained by mean of a so-called Rasch analysis. The results showed that the FIM™ motor items can be compared to the SCIM items from a content but also from a metric point of view. The study showed an advantage in using the SCIM compared to the FIM™ for assessing the functional independence of patients in Spinal Cord Injury rehabilitation.

Keywords

• Spinal Cord Injury
• Functional Independence Measure
• Spinal Cord Independence Measure
• Activities of Daily Living
• Rasch Measurement Model
• Psychometrics