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

Abstract

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.