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

Abstract

BackgroundThe Shoulder Disability Questionnaire (SDQ) demonstrated promising psychometric properties, but currently there is no evidence of an Italian version. ObjectiveTo 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). MethodsThe 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. ResultsThe EFA identified two subscales (activity and participation-psychosocial factors). The internal consistency was supported for activity (α = 0.78), but not for participation-psychosocial subscales (α = 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. ConclusionsThe 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.