Reliability and validity of the Thai version of the Shoulder Pain and Disability Index (Thai SPADI)

BACKGROUND The Shoulder Pain and Disability Index (SPADI) is a good clinical tool to evaluate patients with shoulder pain, but has not been adapted to Thai version. The objectives of this study were to translate the English version and culturally adapt the SPADI to Thai version and to evaluate the internal consistency and construct validity of the Thai SPADI among Thai participants having shoulder pain. METHODS Following the cross-cultural adaptation guidelines stated by the American Association of Orthopedic Surgeons (AAOS) Outcome Committee, the SPADI was translated to Thai version (Thai SPASI). Thai participants with shoulder pain completed the three questionnaires, i.e., the Thai SPADI, bodily pain subscale of the Thai Short Form 36 second version (Thai SF-36 V2) and the Thai version of disabilities of the arm, shoulder, and hand (Thai DASH). Internal consistency of the Thai SPADI was measured using Cronbach's alpha coefficient. Convergent and divergent validity was used to measure construct validity of the Thai SPADI by assessing the correlation of the Thai SPADI with the Thai DASH and bodily pain subscale of the Thai SF-36 V2. RESULTS Of 44 participants, the majority of participants were female (68.2%) and had Bachelor's degree or higher education level (59.1%) with a mean age of 50.4 years (SD 14.3). Cronbach's alpha coefficient of the Thai SPADI in pain subscale, disability subscale and total scale was 0.92, 0.94 and 0.95, respectively. The correlation of the Thai SPADI with the Thai DASH and bodily pain subscale of the Thai SF-36 V was 0.79 (p < 0.001) and -0.49 (p = 001), respectively. CONCLUSIONS The Thai SPADI has excellent internal consistency and moderate to high construct validity to assess shoulder disability among Thais.