Objective: Recommended outcome measures in osteoarthritis are standardized scales identical for each patient. As patient-specific scales are of increasing interest to consider patient's priorities in outcome assessment, this study aims to validate individualized forms of the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) function subscale.
Patients and Methods: WOMAC function subscale data were prospectively obtained from 1218 outpatients with hip or knee osteoarthritis requiring nonsteroidal anti-inflammatory drugs. Patients also rated the importance to get rid of disability in each activity of the WOMAC function subscale and select the 5 activities they considered the most important to be improved upon. After treatment, patients again completed the WOMAC function subscale. Several individualization methods were evaluated: methods whereby the score of each item is multiplied by, or added to, its importance and methods based on the 5 most important activities (WOMAC top 5). Psychometric properties of individualized scales were compared to those of the WOMAC function subscale.
Results: Missing data rate was 11%, 13% and 2% for the WOMAC function, its individualized forms and the WOMAC top 5, respectively. Combining severity and importance of each item did not improve scales' properties. The WOMAC top 5 was the most responsive scale (standardized response mean: 0.96 vs 0.80, p<0.0001).
Conclusion: Because of its better responsiveness, ease of use, low missing data rate and ability to highlight patients' priorities, the WOMAC top 5 could be an interesting tool in therapeutic evaluation in hip or knee osteoarthritis.
- patient reported outcome
- patients' perspectives