Quantifying Neck Fibrosis: Establishing the Domain Structure of the Neck Fibrosis Scale

Objective: We recently described the development of the Neck Fibrosis Scale (NFS). In this submission, we confirm domain structure and validate a scoring system for the NFS.Study Design: Prospective cross-sectional study.Methods: Between January 2020 and December 2021, 127 head and neck cancer patients with varying degrees of cutaneous neck fibrosis completed the original 15 item NFS. Exploratory factor analysis was used to identify optimal groupings with similar underlying factors. The association between the domains of the NFS and various measures of neck morbidity (i.e., construct validity) were assessed using gamma regression.Results: Exploratory factor analysis confirmed 13 of the 15 items from the NFS mapped onto two factors, which were labelled 'physical' and 'emotional' domains. Of the remaining two items, 'energy' did not load uniquely onto one factor and was removed. 'Neck-swelling' did not load on either factor (loadings < 0.3) but was retained within the physical domain based on clinical importance. This resulted in a revised 14-item questionnaire. Internal consistency for these two domains was high (> 0.8, p < 0.01). Both the physical and emotional domains of the revised NFS show strong correlation with the neck dissection impairment index and neck range of motion. The physical domain strongly correlated with neck elasticity (0.902 [95%CI 0.839-0.972], p < 0.01). Patients receiving multimodal therapy had physical domain scores that were 31.6% [95% 13.9-51.8] higher (worse) than unimodal therapy patients.Conclusions: A domain structure and scoring strategy have been developed for the NFS. Future efforts should be directed toward an evaluation of responsiveness.