Reproducibility, validity, and responsiveness of the hip outcome score in patients with end-stage hip osteoarthritis

Objective: To evaluate reproducibility, validity, and responsiveness of the Hip Outcome Score (HOS) in patients with end-stage hip osteoarthritis.

Methods: In a cohort of 157 consecutive patients (mean age 66 years; 79 women) undergoing total hip replacement, the HOS was tested for the following measurement properties: feasibility (percentage of evaluable questionnaires), reproducibility (intraclass correlation coefficient [ICC] and standard error of measurement [SEM]), construct validity (correlation with the Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], Oxford Hip Score [OHS], Short Form 12 health survey, and University of California, Los Angeles activity scale), internal consistency (Cronbach's alpha), factorial validity (factor analysis), floor and ceiling effects, and internal and external responsiveness at 6 months after surgery (standardized response mean and change score correlations).

Results: Missing items occurred frequently. Five percent to 6% of the HOS activities of daily living (ADL) subscales and 20-32% of the sport subscales could not be scored. ICCs were 0.92 for both subscales. SEMs were 1.8 points (ADL subscale) and 2.3 points (sport subscale). Highest correlations were found with the OHS (r = 0.81 for ADL subscale and r = 0.58 for sport subscale) and the WOMAC physical function subscale (r = 0.83 for ADL subscale and r = 0.56 for sport subscale). Cronbach's alpha was 0.93 and 0.88 for the ADL and sport subscales, respectively. Neither unidimensionality of the subscales nor the 2-factor structure was supported by factor analysis. Both subscales showed good internal and external responsiveness.

Conclusion: The HOS is reproducible and responsive when assessing patients with end-stage hip osteoarthritis in whom the items are relevant. However, based on the large proportion of missing data and the findings of the factor analysis, we cannot recommend this questionnaire for routine use in this target group.