For people living with multiple sclerosis, the gap between visible relapses and the silent, cumulative damage accumulating beneath the surface is where long-term disability is increasingly understood to be won or lost. Two blood-based proteins may now offer a practical window into that hidden process — even while patients are on active therapy.
In a longitudinal analysis spanning over nine years and drawing on 2,935 serial serum samples from 420 fingolimod-treated MS patients in the Swiss MS Cohort, researchers evaluated the distinct predictive roles of serum glial fibrillary acidic protein (sGFAP) and serum neurofilament light chain (sNfL). Using Z scores calibrated against a normative reference dataset from 4,297 healthy controls across multiple European and North American sites, the study found that elevated sGFAP Z scores above 0.75 were associated with a 64% increased hazard of experiencing progression independent of relapse activity (PIRA) — the insidious, relapse-unrelated disability accumulation now recognized as a primary driver of long-term MS burden. By contrast, sNfL tracked more closely with relapse activity and reflected whether the disease-modifying therapy was adequately suppressing inflammatory events. Notably, sGFAP concentrations were 13.6% higher in females than males and rose exponentially with age, underscoring the necessity of sex- and age-adjusted normative references.
This work is particularly meaningful because it disentangles what each biomarker is actually measuring in a treated population. The field has long needed tools that can distinguish inflammatory relapse biology from the neurodegenerative substrate underlying PIRA — two mechanistically distinct processes requiring potentially different therapeutic strategies. The dataset's scale and follow-up duration are real strengths, lending the hazard ratios credibility beyond typical single-center studies. Key limitations include the observational design, restriction to a single drug class, and the need for validation across other disease-modifying therapies. Still, this study advances the case that routine blood biomarker monitoring could meaningfully complement MRI surveillance in MS clinical practice — a genuinely incremental but clinically important step forward.