Use of modified Northwick Park Neck Pain Questionnaire in patients with postirradiation neck disability: validation study.

BACKGROUND No available measure exists for postirradiation neck disability. Adoption of the Chinese Northwick Park Neck Pain Questionnaire (NPQ) for patients with postirradiation neck disability was examined in this study. METHODS Eight physiotherapists and five patients were invited to test the validity of the content. Forty-three patients with neck disability were recruited to evaluate test-retest reliability and internal consistency. The level of neck discomfort, range of neck motion and maximal isometric neck muscle strength, and SF-36 health score were measured for construct validity testing. RESULTS The questionnaire had good content validity, a high degree of test-retest reliability, internal consistency (intraclass correlation coefficient [ICC], 0.94; Cronbach's alpha, 0.88), and good construct validity. NPQ correlated significantly with most of the subscores of SF-36 (r(s), -0.43 to - 0.71) and numeric rating scale (r(s) = 0.69). CONCLUSION The modified Chinese NPQ was found to be reliable and valid for the evaluation of postirradiation neck disability.