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, culturally adapting, and validating the Italian version of the Oswestry Disability Index (ODI-I), allowing its use in Italian-speaking patients with low back pain 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 prefinal 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 alpha) and test-retest repeatability (Intraclass Coefficient Correlation), concurrent validity by comparing the ODI-I to Visual Analogue Scale, (Pearson correlation), and construct validity by comparing the ODI-I to Roland Morris Disability Questionnaire, RMDQ, and to Short Form Health Survey, Short Form Health Survey-36 (Pearson correlation).

RESULTS: The authors required a 3-month period before achieving a shared version of the ODI-I. The questionnaire was administered to 126 subjects, showing satisfying acceptability. Factor analysis demonstrated a 1-factor structure (45% of explained variance). The questionnaire showed high internal consistency (alpha = 0.855) and good test-retest reliability (ICC = 0.961). Concurrent validity was confirmed by a high correlation with Visual Analogue Scale (r = 0.73, P < 0.001), Construct validity revealed high correlations with RMDQ (r = 0.819, P < 0.001), and with Short Form Health Survey-36 domains, highly significant with the exception of Mental Health (r = -0.139, P = 0.126).

CONCLUSION: The ODI outcome measure was successfully translated into Italian, showing good factorial structure and psychometric properties, replicating the results of existing language versions of the questionnaire. Its use is recommended in research practice.