Mark Chan Ci En, Dean A. Clair and Stephen J. Edmondston
The purpose of this study was to evaluate the construct and content validity of the Neck Disability Index (NDI) and the Neck Pain and Disability Scale (NPAD) in patients with chronic, non-traumatic neck pain. Twenty patients completed a patient-specific questionnaire, the Problem Elicitation Technique (PET), followed by the NDI and NPAD. Content validity was assessed by comparing the items of the NDI and NPAD with problems identified from the PET. Construct validity of the fixed-item questionnaires was examined by establishing the correlation with each other, and with the PET score.
Both the NDI and the NPAD include most of the functional problems common to this patient group, and display good content validity. The PET is better able to evaluate the problems specific to the individual patient and is therefore measuring a somewhat different construct to the fixed-item questionnaires.
Manual Therapy, 27 September 2008, online article ahead of press