Validation of the Italian version of the client satisfaction with device module of the orthotics and prosthetics users' survey

Background: Information on patient satisfaction with orthosis (PSwO) is crucial for verifying and enhancing orthotic quality, for clinical decision making, and for improving patient's quality of life. Objective: To perform the translation and cross-cultural adaptation into Italian of the recently revised version of the Client Satisfaction with Device (CSD) module of the Orthotics and Prosthetics Users' Survey, and then analyze its psychometric properties using factor and Rasch analyses. Methods: We translated and cross-culturally adapted the revised CSD into Italian (CDS-It) and assessed it in a convenience sample of orthotic-user patients with orthopedic, neurological and rheumatic conditions (N 5 178; 56% men; median age, 62 years). Exploratory factor analysis and Rasch analysis (rating scale model) were used to investigate, respectively, dimensionality and metric properties of the scale. Results: Factor analysis confirmed the substantial unidimensionality of the CSD-It. The rating scale fulfilled the category functioning criteria. All items fitted the Rasch model except #2 ("The weight of my device is manageable") that overfitted the model, and #4 ("It is easy to put on my device") that was underfitting in six stroke patients (i.e. not systematically). The targeting of item difficulty to person ability was out of range. The person separation reliability was 0.70 and Cronbach's alpha 0.73. The residual correlation between items #7 and #8 showed a borderline local dependency. Conclusions: This study confirms the validity of the CSD-It, and provides a useful starting point for further refinement of this outcome measure.