Development and Validation of Crosswalks Between FIM® and SCIM III for Voluntary Musculoskeletal Movement Functions

Area of Science:

• Rehabilitation Medicine
• Biostatistics
• Neuroscience

Background:

• Functional recovery data in spinal cord injury (SCI) is fragmented across databases due to varied measurement instruments.
• A standardized method to link or convert scores between different functional assessment tools is crucial for data aggregation and comparative analysis in SCI research.

Purpose of the Study:

• To develop a crosswalk connecting the voluntary musculoskeletal movement items of the Functional Independence Measure (FIM®) and the Spinal Cord Independence Measure III (SCIM III).
• To facilitate the comparison of functional recovery data in spinal cord injury patients assessed with different instruments.

Main Methods:

• Retrospective datasets from Swiss (n=662), US (n=119), and Canadian (n=133) cohorts were used for developing and validating the crosswalks.
• Three methods were employed: expert panel, equipercentile, and Rasch analysis.
• Correlation between observed FIM® and SCIM III scores was the primary criterion for assessing crosswalk strength, supplemented by secondary criteria like score distributions and subgroup invariance.

Main Results:

• All three crosswalk methods demonstrated strong correlations (r = .897–.972), exceeding the primary criterion of r = .866.
• The equipercentile and Rasch analysis methods yielded the most robust crosswalks based on secondary evaluation criteria.

Conclusions:

• The Rasch-based FIM®/SCIM III crosswalk is recommended due to its foundation in co-calibrated linearized measures, enabling advanced parametric analyses.
• This validated crosswalk will significantly enhance the ability to compare voluntary musculoskeletal functional recovery data across international SCI databases, irrespective of the specific functional measures used.