A multicenter international study on the Spinal Cord Independence Measure, version III : Rasch psychometric validation

Background: A third version of the Spinal Cord Independence Measure (SCIM III), made up of three subscales, was formulated following comments by experts from several countries and Rasch analysis performed on the previous version. Objective: To examine the validity, reliability, and usefulness of SCIM III using Rasch analysis. Design: Multicenter cohort study. Setting: Thirteen spinal cord units in six countries from North America, Europe, and the Middle-East. Subjects: 425 patients with spinal cord lesions (SCL). Interventions: SCIM III assessments by professional staff members. Rasch analysis of admission scores. Main outcome measures: SCIM III subscale match between the distribution of item difficulty grades and the patient ability measurements; reliability of patient ability measures; fit of data to Rasch model requirements; unidimensionality of each subscale; hierarchical ordering of categories within items; differential item functioning across classes of patients and across countries. Results: Results supported the compatibility of the SCIM subscales with the stringent Rasch requirements. Average infit mean-square indices were 0.79-1.06; statistically distinct strata of abilities were 3 to 4; most thresholds between adjacent categories were properly ordered; item hierarchy was stable across most of the clinical subgroups and across countries. In a few items, however, misfit or category threshold disordering were found. Conclusions: The scores of each SCIM III subscale appear as a reliable and useful quantitative representation of a specific construct of independence after SCL. This justifies the use of SCIM in clinical research, including cross-cultural trials. The results also suggest that there is merit in further refining the scale

A new grading for easy and concise description of functional status after spinal cord lesions

Background: Disability scales do not enable the transmission of concise, meaningful and daily function description for clinical purposes. Study design: Cross-sectional statistical analysis of 328 patients' Spinal Cord Independence Measure (SCIM) III item scores (SIS). Objective: To develop a concise and clinically interpretable data-based characterization of daily task accomplishment for patients with spinal cord lesions (SCLs). Setting: Multi-center study at 13 spinal units in 6 countries. Methods: Patients were grouped into clusters characterized by smaller differences between the patients' SIS within the clusters than between their centers, using the k-medoides algorithm. The number of clusters (k) was chosen according to the percent of SIS variation they explained and the clinical distinction between them. Results: Analysis showed that k=8 SIS clusters offer a good description of the patient population. The eight functional clusters were designated as A-H, each cluster (grade) representing a combination of task accomplishments. Higher grades were usually (but not always) associated with patients implementing more difficult tasks. Throughout rehabilitation, the patients' functional grade improved and the distribution of patients with similar functional grades within the total SCIM III score deciles remained stable. Conclusions: A new classification based on SIS clusters enables a concise description of overall functioning and task accomplishment distribution in patients with SCL. A software tool is used to identify the patients' functional grade. Findings support the stability and utility of the grades for characterizing the patients' functional status