Validation of the Neck Disability Index in Serbian Patients With Cervical Radiculopathy.
The purpose of this study was to translate the Neck Disability Index into the Serbian language (NDI-S) and to investigate the validity of this version for use in Serbian population. Fifty patients with cervical radiculopathy were enrolled in the study and completed a multidimensional questionnaire, including NDI-S. Inclusion criteria were ages between 18 and 65 years, Serbian speaking, no cognitive or hearing impairment, sharp and radiating neck and upper extremity pain that has lasted less than 12 months, radiculopathy signs evaluated by electromyoneurography and disc herniation, or spondylotic changes of cervical spine visualized on magnetic resonance imaging. Exclusion criteria were malignancy, previous cervical spine discectomy, trauma of the cervical spine and myelopathy, polyneuropathy, fibromyalgia, and psychiatric disorders. Validity was determined by the correlation of the Neck Disability Index, with pain measured by visual analogue scale, characteristics related to pain, and mental status. Also, factor structure of NDI-S was explored through factor analysis. Reliability was assessed through internal consistency (Cronbach's α and item-total correlations). Correlation analysis between pain and NDI-S showed significant values (P < .01). The NDI-S correlated well with patients mental status (r = 0.421, P < .01). Cronbach's α of NDI-S was 0.85, denoting excellent internal consistency of the questionnaire. Item-total correlations were significant and ranged from 0.328 to 0.789. Factor analysis demonstrated a 2-factor structure with an explained variance of 55%. The NDI-S is a valid questionnaire to measure neck and arm pain related to disability in Serbian patients with cervical radiculopathy.