Reliability and validity study of a Thai version of the Neck Disability Index in patients with neck pain.

OBJECTIVE To evaluate the reliability and validity of the Thai version of the neck disability index (NDI) in neck pain patients. MATERIAL AND METHOD The NDI was translated into Thai. The translation strategy used international standards. Forty-six Thai patients with neck pain were included in the present study. Thai version NDI, short form-36 (SF-36) and visual analogue scale (VAS) were completed by all subjects, twice, one week apart. The reliability and validity were subsequently analyzed. RESULTS Intraclass correlation coefficient score for test retest reliability was 0.986. Cronbach's alpha for internal consistency was calculated as 0.925. For concurrent validity, the relation between NDI and VAS was investigated, the r value was 0.886 (p < 0.001). For construct validity, the relation between NDI and the Thai version of SF-36 was -0.427. The mental health component was highest correlated with NDI. CONCLUSION The Thai version of NDI is a valid and reliable measurement method for evaluating neck pain disability.