Abstract
BACKGROUND: To ensure the validity and therapeutic utility of the Neck disability index (NDI) scale, translations, cultural adaptations and psychometric evidence is necessary. This study aimed to address the absence of a suitable and validated Hindi version of the NDI for the rural population. The specific objectives were to translate, adapt, and evaluate the psychometric properties of the newly developed Hindi version of the NDI. METHODS: Following guidelines provided by the American Association of Orthopedic Surgeons, the original English NDI scale was cross-culturally adapted into Hindi. The adaptation process included translations (forward and backward), expert committee review, pre-testing and cognitive debriefing with 30 individuals experiencing chronic non-specific neck pain. The outcome of this process was the creation of the Hindi version of the NDI, termed NDI-Hi. Subsequently, NDI-Hi was administered to 211 participants with neck pain from multiple centers for psychometric testing. The evaluation involved test-retest reliability over a 48-hour interval, factor analysis, assessment of internal reliability measures, and criterion-related validity by comparing it with the NPAD-Hindi version. RESULTS: The NDI-Hi version exhibited favorable psychometric properties, including good test-retest reliability with an intra-class correlation coefficient (ICC) of 0.87. Internal consistency of the scale was high, indicated by Cronbach's alpha coefficient (α) of 0.96. The standard error of measurement (SEM) was determined to be 2.58, and the minimal detectable change (MDC) was calculated to be 7.15. Furthermore, the NDI-Hi showed significant correlation with the NPAD-Hindi version, with a correlation coefficient (rho) of 0.86, and a p-value of less than 0.001. CONCLUSIONS: The NDI-Hi demonstrated validity and reliability as an outcome tool for assessing neck disability. It can be effectively utilized in clinical practice and research settings involving Hindi-speaking individuals with chronic non-specific neck pain. The adapted scale is particularly well-suited for the rural Northern Indian Hindi-speaking population.