An evaluation of the structural validity of the Work Instability Scale using the Rasch model.

Abstract Objective To examine the measurement properties of the 23-item version of the Work Instability Scale (WIS-23) using Rasch analysis, in a sample of worker compensation claimants with upper extremity disorders. Design Secondary data analysis on the data retrieved from a cross-sectional study. Setting Tertiary care hospital. Participants Patients attending a specialty clinic for workers with upper limb injuries at a tertiary hospital were prospectively enrolled. Interventions Not applicable. Main Outcome Measure(s) WIS-23 Results The study sample contained 392 participants aged 19 to 73 years old with a mean (stand deviation) equal to 47.0 (10.5). There were 148 (37.8%) females, 182 (46.4%) males, and 62 (15.8%) participants for whom gender identification was unavailable. The initial WIS data analysis showed significant misfit from the Rasch model (item-trait interaction x2=293.52, p Conclusion With the application of Rasch analysis, we refined the WIS-23 to produce a 20 item WIS for work-related upper extremity conditions. The 20-item WIS-WREUD demonstrated excellent item and person fit, unidimensionality, acceptable person separation index and local independency. The WIS-20 may provide better measurement properties, although longitudinal psychometric evaluations are needed.