Rasch Analysis of Joint Replacement Version for Hip Disability and Osteoarthritis Outcome in Individuals With Advanced Osteoarthritis of Hip Awaiting Total Hip Arthroplasty Surgery.

Objective: The objective of this study was to examine measurement properties of the Joint replacement version for Hip Disability and Osteoarthritis Outcome Score (HOOS-JR) using Rasch analysis in patients with osteoarthritis of hip (HOA).

Design: Cross-sectional clinical measurement SETTING: Patient outcomes database at a tertiary care hospital PARTICIPANTS: Convenience sampling of patients with HOA scheduled for total hip arthroplasty (N=327) OUTCOME MEASURES AND ANALYSIS: The data for pre-surgery assessments for patients with HOA were extracted from an existing database. Variables extracted included HOOS-JR scores, demographic information (age, sex), health-related data, and anthropometric variables. The assumptions of Rasch model such as the test of fit, fit residuals, ordering of item thresholds, factor structure, DIF, internal consistency and Pearson separation index were examined for the HOOS-JR scores.

Results: The HOOS-JR showed adequate overall fit to the Rasch model, logically ordered response thresholds, no floor or ceiling effects, and high internal consistency (Cronbach's alpha of 0.91). The HOOS-JR did not satisfy the assumption of unidimensionality, albeit the violation of this assumption was marginal (6.12% over 5%). Person-item threshold distribution (difference between person and item means were equal to 0.92 which was less than 1 logit unit) confirmed that the HOOS-JR scores were well targeted.

Conclusions: Given that the violation of unidimensionality for HOOS-JR was marginal, we recommend further studies to validate this finding. Results broadly support the use of HOOS-JR for assessing hip health in patients with HOA.