Cross-diagnostic validity in a generic instrument: an example from the Functional Independence Measure in Scandinavia

This study examines if the Functional Independence Measure (FIM) works the same way for patients with different diagnoses, specifically stroke, spinal cord injury (SCI), and traumatic brain injury (TBI). The researchers used a statistical method called Rasch analysis to see if the FIM scores could be meaningfully compared across these diagnostic groups. They found that the original scoring system of the FIM was problematic and needed adjustment to make valid comparisons across diagnoses.

• 1
  The original seven-category scoring system for the FIM™ motor items was found to be invalid, necessitating extensive rescoring.
• 2
  Differential Item Functioning (DIF) was found for Spinal Cord Injury, compared with the other two diagnoses.
• 3
  After adjustment, it was possible to make appropriate comparisons of sum scores between the three diagnoses.