Development and initial evaluation of the spinal cord injury-functional index

Jette AM, Tulsky DS, Ni P, Kisala PA, Slavin MD, Dijkers MP, Heinemann AW, Tate DG, Whiteneck G, Charlifue S, Houlihan B, Williams S, Kirshblum S, Dyson-Hudson T, Zanca J, Fyffe D. Development and initial evaluation of the Spinal Cord Injury-Functional Index. Objectives: To describe the calibration of the Spinal Cord Injury-Functional Index (SCI-FI) and report on the initial psychometric evaluation of the SCI-FI scales in each content domain. Design: Cross-sectional survey followed by calibration data simulations. Setting: Inpatient and community settings. Participants: A sample of participants (N=855) with traumatic spinal cord injury (SCI) recruited from 6 SCI Model Systems and stratified by diagnosis, severity, and time since injury. Interventions: None. Main Outcome Measure: SCI-FI instrument. Results: Item response theory analyses confirmed the unidimensionality of 5 SCI-FI scales: basic mobility (54 items), fine motor function (36 items), self-care (90 items), ambulation (39 items), and wheelchair mobility (56 items). All SCI-FI scales revealed strong psychometric properties. High correlations of scores on simulated computer adaptive testing (CAT) with the overall SCI-FI domain scores indicated excellent potential for CAT to accurately characterize functional profiles of adults with SCI. Overall, there was very little loss of measurement reliability or precision using CAT compared with the full item bank; however, there was some loss of reliability and precision at the lower and upper ranges of each scale, corresponding to regions where there were few questions in the item banks. Conclusions: Initial evaluation revealed that the SCI-FI achieved considerable breadth of coverage in each content domain and demonstrated acceptable psychometric properties. The use of CAT to administer the SCI-FI will minimize assessment burden, while allowing for the comprehensive assessment of the functional abilities of adults with SCI.