Cross-cultural adaptation, validity and reliability of the Persian translation of the Western Ontario Shoulder Instability Index (WOSI).

Purpose: The Western Ontario Shoulder Instability Index (WOSI) is the most commonly used patient-reported outcome measure to record the quality of life in patients with shoulder instability. The current study aimed to translate the WOSI into the Persian language and evaluate its psychometric properties.

Methods: The translation procedure of the WOSI was performed according to a standard guideline. A total of 52 patients were included in the study and responded to the Persian WOSI, Oxford shoulder score (OSS), Oxford shoulder instability score (OSIS), and disabilities of arm, shoulder and hand (DASH). A sub-group of 41 patients responded for the second time to the Persian WOSI after an interval of 1-2 weeks. The internal consistency, test-retest reliability using intraclass correlation coefficient (ICC), measurement error, minimal detectable change (MDC), and floor and ceiling effect were analyzed. The hypothesis testing method was used to assess construct validity by calculating Pearson correlation coefficient between WOSI and DASH, OSS, and OSIS.

Results: Cronbach's alpha value was 0.93, showing strong internal consistency. Test-retest reliability was good to excellent (ICC = 0.90). There was no floor and ceiling effect. The standard error of measurement and MDC were 8.30% and 23.03%, respectively. Regarding construct validity, 83.3% of the results agreed with hypotheses. High correlations were observed between WOSI and DASH, OSS and OSIS (0.746, 0.759 and 0.643, respectively) indicating excellent validity for the Persian WOSI.

Conclusion: The current study results demonstrated that the Persian WOSI is a valid and reliable instrument and can be used in the clinic and research for Persian-speaking patients with shoulder instability.