The concept of no evidence of disease activity-3 (absence of brain MRI and clinical disease activity; NEDA-3) in multiple sclerosis (MS) reflects disease activity with limited sensitivity. The added value of neurofilament light chain levels in serum (sNfL) to NEDA-3 has not yet been investigated.
To assess whether sNfL allows to identify among patients with and without NEDA-3 status those at higher risk of future disease activity and accelerated brain volume loss.
We analyzed 369 samples from 155 early relapsing-remitting MS patients (SET study). sNfL levels and brain MRI scans were evaluated annually. The comparison of subgroups defined by high or low sNfL (>90th or <90th percentile of healthy controls of the same age) and NEDA-3 status was performed by generalized estimating equation models. Changes in global and regional brain volumes were calculated on three-dimensional T1-weighted scans.
Patients with disease activity (EDA-3) in the preceding year and high sNfL, compared to those with low sNfL, had: a) higher odds of EDA-3 in the following year (87% versus 58%; OR 4.39, 95%-CI:2.18, 8.94; p<0.001), b) greater whole brain volume loss during the following year (0.39%, 95%-CI:-0.63, -0.16; p<0.001) and c) greater whole brain volume loss (0.61%, 95%-CI:-0.66, -0.17; p<0.001) during the preceding year. Accordingly, NEDA-3 patients with high sNfL showed a trend for a return of disease activity (EDA-3) in the following year compared with those with low sNfL (57% versus 31%).
High sNfL levels are associated with increased future risk of disease activity and accelerated brain volume loss. Adding of sNfL improves the prognostic value of the NEDA-3 concept.