RESUMEN
The Neck Disability Index was tested for validity and reliability. Fifty-nine Swedish patients (28 men, 31 women) were included. Twenty patients were in the acute phase after a neck sprain, 19 had chronic neck pain and 20 had no neck pain but had other musculoskeletal symptoms. On 5 occasions, the patients completed the Neck Disability Index, the Disability Rating Index, the MOS 36-item short-form health survey, 2 visual analogue scales, for pain and overall activity and some complementary questions. Levels of sensitivity, test-retest reliability and validity were acceptable. In order to increase specificity, we modified the Neck Disability Index by clarifying that the items only referred to the pain in the neck in 9 of 10 items. Thirty-eight patients (16 men, 22 women) were included in a study of the modified version. Twenty patients with acute neck sprain and 18 with other musculoskeletal symptoms filled out the modified version of the Neck Disability Index, which provided a more specific measure of disability due to neck pain.