Testing the measurement invariance of the University of Washington Self-Efficacy Scale short form across four diagnostic subgroups.

Purpose: The University of Washington Self-Efficacy Scale (UW-SES) was originally developed for people with multiple sclerosis (MS) and spinal cord injury (SCI). This study evaluates the measurement invariance of the 6-item short form of the UW-SES across four disability subgroups. Evidence of measurement invariance would extend the UW-SES for use in two additional diagnostic groups: muscular dystrophy (MD) and post-polio syndrome (PPS).

Methods: Multi-group confirmatory factor analysis was used to evaluate successive levels of measurement invariance of the 6-item short form, the UW-SES: (a) configural invariance, i.e., equivalent item-factor structures between groups; (b) metric invariance, i.e., equivalent unstandardized factor loadings between groups; and (c) scalar invariance, i.e., equivalent item intercepts between groups. Responses from the four groups with different diagnostic disorders were compared: MD (n = 172), MS (n = 868), PPS (n = 225), and SCI (n = 242).

Results: The results of this study support that the most rigorous form of invariance (i.e., scalar) holds for the 6-item short form of the UW-SES across the four diagnostic subgroups.

Conclusions: The current study suggests that the 6-item short form of the UW-SES has the same meaning across the four diagnostic subgroups. Thus, the 6-item short form is validated for people with MD, MS, PPS, and SCI.