ORIGINAL RESEARCH| Volume 103, ISSUE 2, P207-214, February 2022

Linking the Spinal Cord Injury–Functional Index (SCI-FI) to the PROMIS Physical Functioning Item Bank

Published:March 04, 2021DOI:


      • Assessing outcomes using common metrics facilitates cumulative science.
      • The Spinal Cord Injury–Functional Index (SCI-FI) measures physical function after injury.
      • Linked SCI-FI Basic Mobility measure to PROMIS.
      • Researchers can now compare injury-specific mobility scores with PROMIS.



      To link 3 Spinal Cord Injury–Functional Index (SCI-FI) item banks (Basic Mobility, Fine Motor Function, Self-Care) to the Patient-Reported Outcome Measurement Information System (PROMIS) Physical Function (PF) metric.


      Observational study


      Six SCI Model Systems rehabilitation hospitals in the United States.


      Adults with SCI (n=855) and healthy individuals (n=730) (N=1585).


      Not applicable.

      Main Outcome Measures

      Three SCI-FI item banks (Basic Mobility, Fine Motor Function, Self-Care), PROMIS PF v1.0 item bank.


      SCI-FI item banks (including 30 items from the PROMIS PF item bank) were administered to 855 adults with SCI as part of the original SCI-FI development study. The data were used to attempt to link 3 SCI-FI banks to the PROMIS PF metric via 2 item-response theory methods: fixed-parameter calibration and separate calibration. Sixteen items common to SCI-FI and PROMIS and verified as free of differential item functioning were used as anchor items to implement the methods. Of the 3 banks, only SCI-FI Basic Mobility could be linked with sufficient precision to PROMIS PF. Comparisons of actual vs linked PROMIS PF scores and test characteristic curves suggested the fixed-parameter method provided slightly more precision than the separate calibration method.


      The linkage between PROMIS PF and SCI-FI Basic Mobility was considered satisfactory for group-level usage. Score equivalents computed from SCI-FI Basic Mobility will be useful for researchers comparing functional levels in SCI to those observed in other clinical and nonclinical groups (eg, in comparative effectiveness research).


      List of abbreviations:

      CAT (computerized adaptive test), DIF (differential item functioning), IRT (item response theory), NIH (National Institutes of Health), PROM (patient-reported outcome measure), PROMIS (Patient-Reported Outcome Measurement Information System), PROMIS PF (PROMIS Physical Function v1.0), SCI (spinal cord injury), SCI-FI (Spinal Cord Injury–Functional Index), SCI-FI/C (Spinal Cord Injury–Functional Index/Capacity), TCC (test characteristic curve)
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