Spinal Cord Independence Measure, version III: applicability to the UK spinal cord injured population

Abstract

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.