Development and Validation of the Italian Version of the Waddell Chronic Disability Index for People With Low Back Pain

This prospective observational study aims to develop and validate an Italian version of the Waddell Disability Index (WDI-I), a self-administered questionnaire designed to assess disability related to chronic low back pain. Low back pain is a leading cause of disability worldwide, and patient-reported outcome measures are increasingly recognized as essential tools for comprehensive clinical assessment and rehabilitation planning. The study involves a standardized cross-cultural translation process, including forward and backward translations by bilingual translators and review by a panel of expert clinicians, followed by pilot testing. After consensus, the finalized Italian version (WDI-I) will undergo psychometric validation. A total of 115 adult patients with chronic low back pain (≥3 months) will be recruited from two rehabilitation centers. At baseline, participants will complete the WDI-I along with the Numeric Pain Rating Scale (NPRS), the Italian Oswestry Disability Index (ODI-I), and the Italian Pain Catastrophizing Scale (PCS-I). The WDI-I will be re-administered after 7-10 days to assess test-retest reliability. The primary endpoints are internal consistency, reliability, and construct validity of the WDI-I. Statistical analyses will include Cronbach's alpha and item-total correlations for internal consistency, intraclass correlation coefficients (ICC), standard error of measurement (SEM), and minimum detectable change (MDC) for reliability, and Spearman correlation coefficients to evaluate concurrent validity with established pain and disability measures. The study seeks to provide a reliable and valid Italian instrument for assessing disability in individuals with chronic low back pain, facilitating both clinical practice and research