National population-based reference data for the Hip Disability and Osteoarthritis Outcome Score (HOOS)

INTRODUCTION: Interpretation of patient-reported outcome scores such as the Hip Disability and Osteoarthritis Outcome Score (HOOS) can be improved with use of reference values. The aim of the study was to establish population-based reference values for the HOOS’ five subscales and its short-form HOOS-12. MATERIALS AND METHODS: A representative sample of 9997 Danish citizens 18 years and older were identified. The population record-based sample was based on seven predefined age groups and an equal sex distribution within each age group. A national secure electronic system was used to send the HOOS questionnaire and one supplementary question regarding previous hip complaints to all participants. RESULTS: 2277 participants completed the HOOS, 947 women (42%) and 1330 men (58%). The mean HOOS subscale scores were: pain 86.9 (95% CI 86.1–87.7), symptoms 83.7 (95% CI 82.9–84.5), ADL 88.2 (95% CI 87.5–89.0), sport and recreation function 83.1 (95% CI 82.0–84.1), QOL 82.7 (95% CI 81.8–83.6). The youngest age group reported better mean scores in four subscales compared to the oldest age group (pain 91.7 vs. 84.5, mean difference 7.2 95% CI 0.4–14.0), (ADL 94.6 points vs. 83.2, mean difference 11.4 95% CI 4.9–17.8), (sport and recreation function 91.5 points vs. 73.8 points, mean difference 17.7 95% CI 9.0–26.4), (QOL 88.9 points vs. 78.8, mean difference 10.1 points 95% CI 2.0–18.2). Participants with a self-reported hip complaint had worse HOOS scores across all subscales (mean difference range 22.1–34.6). Super obese patients (BMI > 40) had > 12.5 points worse scores across the five HOOS subscales. Results were similar for the HOOS-12. CONCLUSION: This study provides reference values for the HOOS and its short form HOOS-12. Results show that older patients and patients with a BMI over 40 have worse HOOS and HOOS-12 scores that may be of clinical importance in the interpretation of scores both when evaluating potential for improvement and post-treatment results.