Simple shoulder test and Oxford Shoulder Score: Persian translation and cross-cultural validation

Purpose: To translate, culturally adapt, and validate the simple shoulder test (SST) and Oxford Shoulder Score (OSS) into Persian language using a cross-sectional and prospective cohort design. Methods: A standard forward and backward translation was followed to culturally adapt the SST and the OSS into Persian language. Psychometric properties of floor and ceiling effects, construct convergent validity, discriminant validity, internal consistency reliability, test–retest reliability, standard error of the measurement (SEM), smallest detectable change (SDC), and factor structure were determined. Results: One hundred patients with shoulder disorders and 50 healthy subjects participated in the study. The PSST and the POSS showed no missing responses. No floor or ceiling effects were observed. Both the PSST and POSS detected differences between patients and healthy subjects supporting their discriminant validity. Construct convergent validity was confirmed by a very good correlation between the PSST and POSS (r = 0.68). There was high internal consistency for both the PSST (α = 0.73) and the POSS (α = 0.91 and 0.92). Test–retest reliability with 1-week interval was excellent (ICC_agreement = 0.94 for PSST and 0.90 for POSS). Factor analyses demonstrated a three-factor solution for the PSST (49.7 % of variance) and a two-factor solution for the POSS (61.6 % of variance). The SEM/SDC was satisfactory for PSST (5.5/15.3) and POSS (6.8/18.8). Conclusions: The PSST and POSS are valid and reliable outcome measures for assessing functional limitations in Persian-speaking patients with shoulder disorders.