Validity evidence for a modified version of the Orthotics and Prosthetics Users' Survey.

PURPOSE: To evaluate the validity of a modified version of the Orthotics and Prosthetics Users' Survey (OPUS) with persons using different prosthetic and orthotic (P&O) devices.

METHOD: Two-hundred-and-eighty-two adults using prosthesis, orthosis, shoe insoles or orthopaedic shoes completed OPUS. OPUS comprises five modules - Lower and Upper Extremity Functional Status, respectively (LEFS and UEFS), Client Satisfaction with Device and Services, respectively (CSD and CSS), and, Health-Related Quality of Life (HRQoL). Eight new items were added to LEFS and six to UEFS. Rasch analysis was used for data analyses.

RESULTS: Rating scales functioned satisfactory after some modifications. All modules demonstrated a ceiling effect. Unidimensionality was satisfactory after deleting some items and dividing HRQoL into two subscales, although somewhat weak on CSD and CSS. Item reliability was excellent for all modules and person reliability good for all but CSD and CSS. Some items demonstrated differential item functioning related to sex and age, but the impact on person measures was small.

CONCLUSIONS: This study supports the validity of a modified version of OPUS for persons using different P&O devices, but also reveals limitations to be addressed in future studies. OPUS could be useful in clinical rehabilitation and research to evaluate P&O outcomes.