Does serum neurofilament light chain measurement influence therapeutic decisions in multiple sclerosis?

Background: The assessment of serum neurofilament light chain (sNfL) concentration in multiple sclerosis (MS) is a useful tool for predicting clinical outcomes and assessing treatment response. However, its use in clinical practice is still limited. We aimed to assess how measurement of sNfL influences neurologists' treatment decisions in MS. Methods: We conducted a cross-sectional, web-based study in collaboration with the Spanish Society of Neurology. Neurologists involved in MS care were presented with different simulated case scenarios of patients experiencing either their first demyelinating MS event or a relapsing-remitting MS. The primary outcome was therapeutic inertia (TI), defined as the absence of treatment initiation or intensification despite elevated sNfL levels. Nine cases were included to estimate the TI score (range 0-9, where higher values represented a higher degree of TI). Results: A total of 116 participants were studied. Mean age (standard deviation-SD) was 41.9 (10.1) years, 53.4 % male. Seventy-eight (67.2 %) were neurologists fully dedicated to the care of demyelinating disorders. Mean (SD) TI score was 3.65 (1.01). Overall, 92.2 % of participants (n = 107) presented TI in at least 2/9 case scenarios. The lack of full dedication to MS care (p = 0.014), preference for taking risks (p = 0.008), and low willingness to adopt evidence-based innovations (p = 0.009) were associated with higher TI scores in the multivariate analysis after adjustment for confounders. Conclusion: TI was a common phenomenon among neurologists managing MS patients when faced with the decision to initiate or escalate treatment based on elevated sNfL levels. Identifying factors associated with this phenomenon may help optimize treatment decisions in MS care.