Spanish version of SPADI (shoulder pain and disability index) in musculoskeletal shoulder pain: a new 10-items version after confirmatory factor analysis

BACKGROUND The Shoulder Pain and Disability Index (SPADI) is a tool designed to evaluate the impact of shoulder pathology. The aim of this study was to cross culturally adapt a Spanish version of the SPADI for Spanish population with a musculoskeletal shoulder pain, and to determine the psychometric properties of this instrument using confirmatory factor analysis (CFA). METHODS Cross-cultural adaptation was performed according to the international guidelines. To assess factor structure, a confirmatory factor analysis was done. Internal consistency was measured using Cronbach's alpha. Item-total and inter-item correlations were assessed. Pearson and Spearman correlations were calculated to assess the convergent validity between SPADI and quick-DASH. RESULTS A new Spanish version of SPADI was achieved. The original SPADI factor structure was tested by CFA, obtaining a poor fit: relative chi-square (χ2/df) 3.16, CFI 0.89, NFI 0.92, and RMSEA 0.10 (90 % CI 0.08 to 0.12). An additional model was tested, after deleting items which have had a poor adjustment in the model (1, 11, and 12), obtaining the best fit: relative chi-square (χ2/df) of 1.94, CFI 0.98, NFI 0.95, GFI 0,95, and RMSEA 0.06 (90 % CI 0.04 to 0.09). The analysis confirmed the bidimensional structure (pain and disability subscales). A correlation Spearman's Rho coefficient of 0.752 (p < 0.0001) and a Cronbach's alpha of 0.90 were obtained. CONCLUSIONS This study validated a new 10-items version of SPADI for Spanish population with musculoskeletal shoulder pain providing a patient reported outcome measure that could be used in both clinical practice and research.