Agreement between Original and Rasch-Approved Neck Disability Index

Background: Given the high prevalence of neck pain, the neck disability index (NDI) has been used widely to evaluate patient status and treatment outcomes. Modified versions have been proposed as solutions to measurement deficits in the NDI. However, the original 10-item NDI scored out of 50 is still the commonly administered. Examining the extent of agreement between traditional and Rasch-based versions using Bland-Altman (B&A) plots will …