Mapping of Neck Disability Index domains linked to the international classification of functioning and disability

Objective: This study aims to link NDI items to CIF using specific and up-to-date linking rules. Methods: It is a measurement properties analysis study in which two evaluators performed the link between NDI and CIF, both with experience in CIF taxonomy and NDI application. Thus, ten binding rules developed and updated specifically for binding the ICF to other instruments were applied. Results: The Kappa coefficient determined the level of agreement between the evaluators with a confidence interval of 95%. All NDI items were linked to ICF codes; there was no need to use the term “non-definable.” The degree of agreement between the evaluators about the domains and the categories of the ICF's first, second, and third levels was almost perfect. Conclusion: Therefore, the NDI is well linked to the codes related to the ICF domains' Activity, Participation, Functions, and Structure. However, no concepts related to contextual factors were identified.