Translation and validation of the Western Ontario Osteoarthritis of the Shoulder (WOOS) index – the Danish version

Jeppe V Rasmussen,¹ John Jakobsen,² Bo S Olsen,¹ Stig Brorson<sup>1

1</sup>Department of Orthopedic Surgery, Herlev University Hospital, Herlev, Denmark; ²Department of Orthopedic Surgery, Aalborg University Hospital, Thisted, Denmark

Background and purpose: The Western Ontario Osteoarthritis of the Shoulder (WOOS) index is a patient-reported, disease-specific questionnaire for the measurement of the quality-of-life in patients with osteoarthritis. The purpose of this study was to describe the process used to translate the WOOS into Danish and to test the translation in a Danish population, in terms of validity, reliability, and responsiveness.
Material and methods: The translation of the WOOS was done according to international standardized guidelines. The psychometric properties were tested in 20 consecutive patients. The eligibility criteria were: a diagnosis of osteoarthritis without symptomatic rotator cuff pathology and treated with primary shoulder replacement. Patients were excluded only in the case of other pathology of the upper extremity or in the case of cognitive or linguistic impairment compromising the ability to complete the questionnaires.
Results: The Pearson's correlation coefficient between the WOOS and the Constant-Murley score (CMS), preoperatively was 0.62 (P = 0.004) and the correlation between the changes of score for the WOOS and CMS was 0.73 (P < 0.001). The correlation coefficient between the WOOS and the CMS, SF-36, and the Oxford Shoulder Score postoperatively was 0.82 (P < 0.001), 0.48 (P = 0.03), and 0.82 (P < 0.001), respectively. There were no floor and ceiling effects. The Cronbach's alpha was 0.98. The intraclass correlation coefficient between test and retest was 0.96. The standardized response mean was 1.41, and effect size was 2.32.
Conclusion: We have shown that the Danish version of the WOOS, translated according to international standardized guidelines, has substantial statistical and clinical psychometric properties at the same level as was described for the original version.

Keywords: outcome assessment, cross-cultural adaption, questionnaire