The development of a disease-specific quality of life measurement tool for osteoarthritis of the shoulder: The Western Ontario Osteoarthritis of the Shoulder (WOOS) index

Objective The purpose of this study was to develop and validate a disease-specific quality of life measurement tool for osteoarthritis (OA) of the shoulder. Methods An instrument which could be used as the primary outcome measure in clinical trials involving patients with OA of the shoulder was developed using a specific methodological protocol: (1) identification of a specific patient population; (2) item generation; (3) item reduction; (4) pre-testing of the prototype questionnaire and (5) determining the validity, reliability and responsiveness of the final questionnaire. Results The final instrument contains 19 items, each with a visual analog response option for the four domains (six questions for pain and physical symptoms, five questions for sport, recreation and work, five questions for lifestyle function and three questions for emotional function). Ten of the 19 questions had not been identified previously on other shoulder measurement tools. The instrument proved to be valid by demonstrating predicted correlations with previously published shoulder measures, global health status measure and range of motion. The new instrument was also more responsive than other shoulder measurement tools, a global health status measure and range of motion. Conclusions Since the patient's own perception of changes in health status is the most important indicator of the success of treatment we suggest that this measurement tool be used as the primary outcome in clinical evaluation of various treatments for OA of the shoulder and monitoring patients over time.