The neck pain and disability scale: test-retest reliability and construct validity.

OBJECTIVE This research established test-retest reliability and construct validity for the Neck Pain and Disability Scale (NPAD). METHODS Two groups of patients with neck pain completed the NPAD. The first group filled out the scale twice before treatment, whereas the second completed it with a number of other outcome measures once a month for 4 months, for evaluation of treatment with injections. RESULTS The reliability coefficient (r2 = 0.93) calculated from the data for the first group of patients indicated high test-retest reliability. Construct validity was demonstrated with the second group when the NPAD was compared with a number of other pain measures and found to have a larger treatment effect. The Neck Pain and Disability Scale factor scores also indicated that treatment effects varied across the four factors. CONCLUSIONS The NPAD is a stable and responsive measure for patients with neck pain. The Neck Pain and Disability Scale factor scores are useful in identifying treatment effects on the specific dimensions involved in the pain experience.