Development of the Italian version of the Oswestry Disability Index, ODI-I. A cross-cultural adaptation, reliability and validity study

Study Design. Evaluation of the psychometric properties of a translated, culturally adapted questionnaire. Objective. Translating, cul¬turally adapting, and validating the Italian version of the Oswestry Disability Index (ODI-I), allowing its use in Italian-speaking low back pain patients inside and outside Italy. Summary of Background Data. Growing attention is devoted to standardized outcome measures to improve interventions for low back pain. A translated form of the ODI in patients with low back pain has never been validated within the Italian population. Methods. The ODI-I questionnaire was developed involving forward-backward translation, final review by an expert committee and test of the pre-final version to establish as better as possible proper correspondence with the original English latest version (2.1a). Psychometric testing included factor analysis, reliability by internal consistency (Cronbach’s alpha) and test-retest repeatability (Intraclass Coefficient Correlation), concurrent validity by comparing the ODI-I to Visual Analogue Scale, VAS (Pearson’s correlation), and construct validity by comparing the ODI-I to Roland Morris Disability Questionnaire, RMDQ, and to Short Form Health Survey, SF-36 (Pearson’s correlation). Results. The Authors required a three-month period before achieving a shared version of the ODI-I. The questionnaire was administered to 126 subjects, showing good acceptability. Factor analysis demonstrated a one-factor structure (45% of explained variance). The questionnaire showed high internal consistency (Cronbach’s alpha 0.855) and good test-retest reliability (ICC=0.961). Concurrent Validity was confirmed by a high correlation with VAS (r = 0.73, p<0.001), Construct Validity revealed high correlations with RMDQ (r = 0.819, p<0.001), and with single SF-36 domains scores, highly significant with the exception of mental health domain (r = -0.139, p=0.126). Conclusion. The ODI-I outcome measure was successfully translated into Italian, showing good factorial structure and psychometric properties, replicating the results of already existing language versions of the scale. Its use is recommended in research practice.