Objectives: To assess neurofilament light chain serum (sNfL) levels in patients with secondary progressive multiple sclerosis (SP-MS).
Methods: Using a single molecule array, we analyzed sNfL levels in a cross-sectional cohort study of 153 patients with SP-MS hospitalized for rehabilitation in a clinic specialized in the care for patients with multiple sclerosis (MS). In addition, we investigated the correlation of disease activity with sNfL levels in 36 patients with relapsing-remitting MS (RR-MS).
Results: Mean sNfL levels in patients with SP-MS were consistently elevated when compared with age-matched controls and patients with RR-MS. In SP-MS, age dependency of sNfL levels was pronounced, whereas patients with RR-MS younger than 41 years without recent disease activity were not distinguishable from age-matched healthy controls. In a multivariate analysis, clinical disability was a risk factor for elevated sNfL levels in SP-MS, whereas no correlation with comorbidities, such as cardiovascular disease, diabetes mellitus, smoking status, or vitamin D serum levels, could be detected.
Discussion: These findings highlight that measurement of sNfL levels represents a useful tool to assess the extent of neuroaxonal damage as a surrogate for clinical progression in patients with SP-MS, when age and disease activity as major confounders are taken into account.