Cross-cultural adaptation and psychometric evaluation of the Malay version of the Neck Disability Index

Purpose: Translating the Neck Disability Index (NDI) into the Malay language (NDI-M); evaluation of psychometric properties in patients with neck pain.Methods: The NDI-M was translated according to established guidelines. In the first visit, 120 participants completed the NDI-M, visual analogue scale (VAS) for pain and demographic details. 98 participants returned to complete similar questionnaires and the Global Rating of Change (GRoC) scale. The NDI-M was evaluated for internal consistency, test-retest reliability, content validity, construct validity and responsiveness.Results: The NDI-M demonstrated excellent internal consistency (Cronbach's α = 0.84) and good test-retest reliability (ICC_2,1 = 0.79). Content validity was confirmed with no floor or ceiling effects. Construct validity was established revealing three-factor subscales explaining 68% of the total variance. The NDI-M showed a moderate correlation with VAS (R_p = 0.49, p < 0.001). Regarding responsiveness, a moderate correlation between NDI-M change scores and VAS change scores was found (R_p = 0.40, p < 0.001). However, there was no significant correlation between NDI-M with GRoC (R_s = 0.11, p = 0.27).Conclusions: The NDI-M is a reliable and valid tool to measure functional outcomes in patients with neck pain. It is responsive in detecting changes in pain intensity during a patient's rehabilitation journey.Implications for rehabilitationThe NDI was translated into the Malay language and culturally adapted for Malay-speaking patients with neck pain.The NDI-M demonstrated an excellent level of internal consistency and good test-retest reliability. It demonstrated content and construct validity, with three-factor subscales, and moderate responsiveness for pain intensity.The NDI-M is a reliable, valid and responsive instrument to measure functional limitations in patients with neck pain for rehabilitation.