Study design: Cross-cultural adaptation and cross-sectional psychometric testing in a convenience sample of patients with neck pain.
Objective: To translate and cross-culturally adapt the Neck Disability Index (NDI) into a Taiwanese version and to assess the psychometric properties.
Summary of background data: The Taiwanese NDI has not been developed or validated.
Methods: The NDI was first translated and culturally adapted to the Taiwanese version. The test-retest reliability within 1 week was examined (n = 32). The factor structure was assessed by confirmatory factor analysis (n = 137). The construct validity was assessed by examining the relationship between the NDI and other well-known measures (n = 137).
Results: The Taiwanese version was successfully translated and cross-culturally adapted. The internal consistency was excellent, with Cronbach α = 0.89. High test-retest reliability was demonstrated with intraclass correlation coefficients of 0.87. The minimal detectable change was 8.74. The two-factor model (pain and function factors) was better than the one-factor model, with higher factor loadings and better goodness-of-fit statistics. The convergent validity was supported by moderate correlation of the pain factor with the Visual Analogue Scale (|rho| = 0.45), and high correlation of the function factor with the physical component summary of the Short-From 36 (SF-36) (|rho| = 0.60).
Conclusion: The Taiwanese NDI is a reliable and valid disease-specific measure for assessment of pain and functional status in patients with neck pain.
Level of evidence: 3.