Spinal Cord Independence Measure, version III: applicability to the UK spinal cord injured population.
OBJECTIVE
To examine the validity, reliability and usefulness of the Spinal Cord Independence Measure for the UK spinal cord injury population.


DESIGN
Multi-centre cohort study.


SETTING
Four UK regional spinal cord injury centres.


SUBJECTS
Eighty-six people with spinal cord injury.


INTERVENTIONS
Spinal Cord Independence Measure and Functional Independence Measure on admission analysed using inferential statistics, and Rasch analysis of Spinal Cord Independence Measure.


MAIN OUTCOME MEASURES
Internal consistency, inter-rater reliability, discriminant validity; Spinal Cord Independence Measure subscale match between distribution of item difficulty and patient ability measurements; reliability of patient ability measures; fit of data to Rasch model; unidimensionality of subscales; hierarchical ordering of categories within items; differential item functioning across patient groups.


RESULTS
Scale reliability (kappa coefficients range 0.491-0.835; (p < 0.001)), internal consistency (Cronbach's alpha 0.770 and 0.780 for raters), and validity (Pearson correlation; p < 0.01) were all significant. Spinal Cord Independence Measure subscales compatible with stringent Rasch requirements; mean infit indices high; distinct strata of abilities identified; most thresholds ordered; item hierarchy stable across clinical groups and centres. Misfit and differences in item hierarchy identified. Difficulties assessing central cord injuries highlighted.


CONCLUSION
Conventional statistical and Rasch analyses justify the use of the Spinal Cord Independence Measure in clinical practice and research in the UK. Cross-cultural validity may be further improved.