Cross-cultural adaptation, reliability, and validity of the Italian version of the Shoulder Disability Questionnaire

Background: The Shoulder Disability Questionnaire (SDQ) demonstrated promising psychometric properties, but currently there is no evidence of an Italian version. Objective: To cross-culturally adapt the Italian version of the SDQ (SDQ-I) and to explore its psychometric properties in patients with non-specific shoulder pain (SP). Methods: The SDQ-I was translated according to international guidelines and administered to 105 patients with SP. The SDQ-I scores were compared with Disabilities of the Arm, Shoulder, and Hand Questionnaire (DASH), Numerical Pain Rating Scale (NPRS), and 36-item Short Form Health Survey (SF-36). Structural validity (Exploratory Factor Analysis [EFA]), internal consistency (Cronbach's alpha), test-retest reliability (Intraclass Correlation Coefficient [ICC]), measurement error (Standard Error of the Measurement [SEM], Minimal Detectable Change [MDC]), and construct validity (hypothesis testing with correlation of the DASH, NPRS, and SF-36) were explored. Results: The EFA identified two subscales (activity and participation-psychosocial factors). The internal consistency was supported for activity (alpha = 0.78), but not for participation-psychosocial subscales (alpha = 0.45). Both subscales demonstrated high test-retest reliability (ICC = 0.97 [95%CI = 0.96-0.98] and ICC = 0.95 [95%CI = 0.93-0.97]), a SEM of 5.8% and 7.0%, and a MDC of 15% and 19% for the first and second subscale, respectively. Construct validity was satisfactory, as >75% of the expected correlations were met for each subscale. Conclusions: The SDQ-I was successfully cross-cultural adapted into Italian and proved to be valid for patients with non-specific SP, but its reliability should be further assessed, as internal consistency of the participation-psychosocial subscale showed some psychometric flaws. Further research is needed to refine the instrument.