Renal function's impact on serum neurofilament levels in patients with multiple sclerosis: an exploratory analysis

Background sNfL, a promising biomarker for neuroaxonal damage in Multiple Sclerosis (MS), requires cautious interpretation due to several comorbidity influences. Objectives To investigate the impact of renal function on sNfL levels in MS patients. Methods This retrospective study stratified patients by MS clinical phenotype, acute inflammatory activity (AIA) status-defined as relapse or gadolinium-enhancing lesions within 90 days of sample collection-renal function, assessed by estimated glomerular filtration rate (eGFR), and age (< 40 years, 40-60 years, > 60 years). Comparative analysis of sNfL levels across these groups was performed. The sNfL-eGFR relationship was examined using linear and non-linear regression models, with the best fit determined by R2 and the F estimator. Results Data from 2933 determinations across 800 patients were analyzed. Patients with renal insufficiency (RI) (eGFR < 60 mL/min/1.73 m2) and mild renal impairment (MDRF) (eGFR 60-90 mL/min/1.73 m2) showed significantly higher sNfL levels compared to those with normal renal function, a pattern also observed in age groups 40 years and older. No significant differences were found between MDRF patients and those with AIA. Among RI patients, no differences in sNfL levels were observed between relapsing-remitting and progressive MS phenotypes. A regression S-Curve model was identified as the best fit, illustrating a marked increase in sNfL levels beginning at an eGFR of approximately 75 mL/min/1.73 m2. Discussion Caution is advised when interpreting sNfL levels for monitoring MS in patients with impaired renal function.