Reliability, validity, and responsiveness of the Persian version of Shoulder Activity Scale in a group of patients with shoulder disorders.

PURPOSE: The aim of this methodological study was to cross-culturally translate the Shoulder Activity Scale (SAS) into the Persian and determine its clinimetric properties including reliability, validity, and responsiveness in patients with shoulder disorders.

METHOD: Persian version of the SAS was obtained after standard forward-backward translation. Three questionnaires were completed by the respondents: SAS, shoulder pain and disability index (SPADI), and Short-Form 36 Health Survey (SF-36). The patients completed the SAS, 1 week after the first visit to evaluate the test-retest reliability. Construct validity was evaluated by examining the associations between the scores on the SAS and the scores obtained from the SPADI, SF-36, and age of the patients. To assess responsiveness, data were collected in the first visit and then again after 4 weeks physiotherapy intervention. Test-retest reliability and internal consistency were assessed using Intra-class Correlation Coefficient (ICC) and Cronbach's alpha, respectively. To evaluate construct validity, Spearman's rank correlation was used. The ability of the SAS to detect changes was evaluated by the receiver-operating characteristics method.

RESULTS: No problem or language difficulties were reported during translation process. Test-retest reliability of the SAS was excellent with an ICC of 0.98. Also, the marginal Cronbach's alpha level of 0.64 was obtained. The correlation between the SAS and the SPADI was low, proving divergent validity, whereas the correlations between the SAS and the SF-36/age were moderate proving convergent validity. A marginally acceptable responsiveness was achieved for the Persian SAS.

CONCLUSIONS: The study provides some evidences to support the test-retest reliability, internal consistency, construct validity, and responsiveness of the Persian version of the SAS in patients with shoulder disorders. Therefore, it seems that this instrument is a useful measure of shoulder activity level in research setting and clinical practice.

IMPLICATIONS FOR REHABILITATION: The shoulder activity scale (SAS) is a reliable, valid, and responsive measure of shoulder activity level in Persian-speaking patients with different shoulder disorders. The results on clinimetric properties of the Persian SAS are comparable with its original, English version. Persian version of the SAS can be used in "clinical" and "research" settings of patients with shoulder disorders.