Cross-cultural adaptation and validation of the italian version of the Spine Functional Index

SUMMARY Purpose. The Spine Functional Index (SFI) was developed to assess spinal function based on the idea of a single kinetic chain concept for the entire spine. The SFI has been translated into Spanish, Turkish, Simplified Chinese, Korean, Persian and Polish with accepted psychometric properties. The aim of this study is to translate and culturally adapt the SFI into Italian language and to verify the construct validity and reliability of this version. Methods. The English version of the SFI has been translated according to international guidelines. The measurement properties (construct validity and reliability) have been tested according to COSMIN checklists. A total of 230 patients were included in this study. Exploratory Factor Analysis (EFA) was used to analyze structural validity. Cronbach’s α was calculated to assess the internal consistency and the Intraclass Correlation Coefficient (ICC) was calculated to estimate the reliability. The Functional Rating Index (FRI), the Oswestry Disability Index (ODI), the Neck Disability Index (NDI), the EuroQol Health Questionnaire 5 Dimensions (EQ-5D) and a Visual Analogue Scale (VAS) were used to assess the validity of the construct. Results. All the items were similar in meaning to the originals. EFA showed a mono-factorial structure. Cronbach’s α was 0.743 and the ICC was 0.914 (95%CI 0.864-0.945). The Pearson’s Correlation Coefficient showed significant correlations (p < 0.01) between SFI and FRI, ODI, NDI, EQ-5D and VAS items. Conclusions. The study provided an Italian version of the SFI with good reliability and construct validity. The results of current study suggest that the Italian version of the SFI can be applied by physicians and researchers to measure the spine functional status in Italian population.