Supplemental PowerPoint Slides Measurement properties of the Norwegian version of the Neck Disability Index in chronic neck pain Jan Børre Johansena, Nada Andelica,b, Eva Bakkec, Erik Bautz Holtera,b, Anne Marit Mengshoelc, Cecilie Røea,b. aDepartment of Physical Medicine and Rehabilitation, Oslo University Hospital, Ulleval, Norway bFaculty of Medicine, University of Oslo, Norway cDepartment of Health Sciences, Institute of Health and Society, University of Oslo, Norway Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited

Norwegian version of the Neck Disability Index Supplemental PowerPoint Slides Norwegian version of the Neck Disability Index In the present paper the Rasch model was used to analyze the unidimensionality, scaling and invariance of the NDI across gender, age, education and work status in chronic neck pain patients in specialized care. Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited

Supplemental PowerPoint Slides The data did not fit the Rasch model. Three items (lifting, reading, driving) had disordered response thresholds. The pain, headache and sleep items did not fit the Rasch model. Differential item function was detected for work status. Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited

The Neck Disability Index Conclusions Supplemental PowerPoint Slides The Neck Disability Index Conclusions The Rasch analysis lends support to: the unidimensionality of seven items of the NDI its usefulness in capturing the neck patients’ disability the NDI being generally robust to external factors. Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited