Serum Neurofilament Light concentrations are not associated with renal function in secondary progressive multiple sclerosis

Abstract Background Neurofilament Light (NFL) is a promising biomarker of neuroaxonal injury. Its utility may be improved by expression relative to age-matched controls and by adjusting for other covariates, such as body mass index. It has recently been suggested that renal function may modulate the rate of clearance of NFL from circulation, which if confirmed would make renal function an important additional covariate to take into account when interpreting NFL data in research or clinical settings. Here we explore the relationship between renal function and NFL in a cohort of patients with secondary progressive multiple sclerosis (SPMS). Methods We examined data from patients with SPMS who took part in the MS-STAT randomised controlled trial. We use multivariable linear regression to explore the relationship between serum NFL and renal function, and additionally to examine whether including renal function as a covariate improves the ability of NFL to predict the subsequent rate of whole brain atrophy. Results Data on renal function and serum NFL was available for 122 patients. Mean eGFR 88 ml/min/1.73 m2 (range 38.2–121.9). We found no evidence to support a relationship between renal function and serum NFL in this cohort. Furthermore, the inclusion of eGFR as a covariate in models assessing the relationship between NFL and the rate of whole brain atrophy had no significant effect upon the relationships observed. Conclusions We find no evidence for a relationship between renal function and NFL in a cohort of patients with secondary progressive multiple sclerosis. We hypothesise that the previously observed relationships between NFL and renal function related to associations between renal function and subclinical neuropathology, rather than due to modulating clearance of NFL from the circulation, but further research would be required to confirm such mechanisms.