ImportanceThere is a lack of validated biomarkers for disability progression independent of relapse activity (PIRA) in multiple sclerosis (MS).ObjectiveTo determine how serum glial fibrillary acidic protein (sGFAP) and serum neurofilament light chain (sNfL) correlate with features of disease progression vs acute focal inflammation in MS and how they can prognosticate disease progression.Design, Setting, and ParticipantsData were acquired in the longitudinal Swiss MS cohort (SMSC; a consortium of tertiary referral hospitals) from January 1, 2012, to October 20, 2022. The SMSC is a prospective, multicenter study performed in 8 centers in Switzerland. For this nested study, participants had to meet the following inclusion criteria: cohort 1, patients with MS and either stable or worsening disability and similar baseline Expanded Disability Status Scale scores with no relapses during the entire follow-up; and cohort 2, all SMSC study patients who had initiated and continued B-cell–depleting treatment (ie, ocrelizumab or rituximab).ExposuresPatients received standard immunotherapies or were untreated.Main Outcomes and MeasuresIn cohort 1, sGFAP and sNfL levels were measured longitudinally using Simoa assays. Healthy control samples served as the reference. In cohort 2, sGFAP and sNfL levels were determined cross-sectionally.ResultsThis study included a total of 355 patients (103 [29.0%] in cohort 1: median [IQR] age, 42.1 [33.2-47.6] years; 73 female patients [70.9%]; and 252 [71.0%] in cohort 2: median [IQR] age, 44.3 [33.3-54.7] years; 156 female patients [61.9%]) and 259 healthy controls with a median [IQR] age of 44.3 [36.3-52.3] years and 177 female individuals (68.3%). sGFAP levels in controls increased as a function of age (1.5% per year; P < .001), were inversely correlated with BMI (−1.1% per BMI unit; P = .01), and were 14.9% higher in women than in men (P = .004). In cohort 1, patients with worsening progressive MS showed 50.9% higher sGFAP levels compared with those with stable MS after additional sNfL adjustment, whereas the 25% increase of sNfL disappeared after additional sGFAP adjustment. Higher sGFAP at baseline was associated with accelerated gray matter brain volume loss (per doubling: 0.24% per year; P < .001) but not white matter loss. sGFAP levels remained unchanged during disease exacerbations vs remission phases. In cohort 2, median (IQR) sGFAP z scores were higher in patients developing future confirmed disability worsening compared with those with stable disability (1.94 [0.36-2.23] vs 0.71 [−0.13 to 1.73]; P = .002); this was not significant for sNfL. However, the combined elevation of z scores of both biomarkers resulted in a 4- to 5-fold increased risk of confirmed disability worsening (hazard ratio [HR], 4.09; 95% CI, 2.04-8.18; P < .001) and PIRA (HR, 4.71; 95% CI, 2.05-9.77; P < .001).Conclusions and RelevanceResults of this cohort study suggest that sGFAP is a prognostic biomarker for future PIRA and revealed its complementary potential next to sNfL. sGFAP may serve as a useful biomarker for disease progression in MS in individual patient management and drug development.

Objective: Serum neurofilament light (sNfL) is a promising marker for neuro-axonal damage and it is now well known that its levels also increase with higher age. However, the effect of other determinants besides age is still poorly investigated. We therefore aimed to identify factors influencing the sNfL concentration by analysing a large set of demographical, life-style and clinical variables in a normal aging cohort. Methods: sNfL was quantified by single molecule array (Simoa) assay in 327 neurologically inconspicuous individuals (median age 67.8±10.7 years, 192 female) who participated in the Austrian Stroke Prevention Family Study (ASPS-Fam). Random forest regression analysis was used to rank the association of included variables with sNfL in the entire cohort and in age-stratified subgroups. Linear regression then served to identify factors independently influencing sNfL concentration. Results: Age (β=0.513, p<0.001) was by far the most important factor influencing sNfL, which was mainly driven by individuals ≥60 years. In age stratified sub-groups, body mass index (BMI) (β=-0.298, p<0.001) independently predicted sNfL in individuals aged 38-60 years. In individuals ≥60 years, age (β=0.394, p<0.001), renal function (β=0.376, p<0.001), blood volume (β=-0.198, p=0.008) and high density lipoprotein (HDL) (β=0.149, p=0.013) were associated with sNfL levels. Conclusions: Age is the most important factor influencing sNfL concentrations, getting increasingly relevant in elderly people. BMI further influences sNfL levels, especially at younger age, whereas renal function gets increasingly relevant in the elderly.

Background: Serum neurofilament light chain (sNfL) levels and peripapillary retinal nerve fiber layer (pRNFL) are both emerging biomarkers of neuro-axonal damage in multiple sclerosis (MS). However, data on the relation between sNfL and pRNFL are scarce. Objective: We aimed to determine the relation of sNfL levels with pRNFL thinning in a large cohort of relapsing–remitting (RR) MS patients. Methods: We identified 80 patients from a prospective, 3-year observational study on retinal changes in RRMS with annual blood samples available. sNfL levels were measured using single-molecule array (SimoaTM) assay. Annualized loss of pRNFL (aLpRNFL) was determined by individual linear regression models. Correlations between single and repeated sNfL levels and aLpRNFL were analyzed using multivariate linear regression and mixed-effect models. Results: After correction for sex, age, and baseline sNfL, an sNfL increase of 10 pg/mL was associated with an aLpRNFL of −0.7 µm (95% confidence interval (CI): (−1.3, −0.2), p < 0.001). Patients with ⩾2 sNfL measurements >75th percentile displayed higher aLpRNFL (2.2 µm, standard deviation (SD) 0.6) compared to patients with no sNfL measure >75th percentile (0.4 µm, SD 0.2, p < 0.001). Between 15% and 20% of the aLpRNFL variance could be predicted from sNfL levels. Conclusion: sNfL levels contribute to the prediction of retinal thinning in patients with RRMS, strengthening its value as a biomarker of neuro-axonal damage.

BackgroundEfficacy of vaccines and disease activity linked to immunization are major concerns among people with multiple sclerosis (pwMS).ObjectiveTo assess antibody responses to seasonal influenza antigens and vaccine-associated neuroaxonal damage utilizing serum neurofilament light chain (sNfL) in pwMS receiving dimethyl fumarate (DMF).MethodsIn this prospective study, the 2020/2021 seasonal tetravalent influenza vaccine was administered to 20 pwMS treated with DMF and 15 healthy controls (HCs). The primary endpoints were responder rate of strain-specific antibody production (seroconversion or significant (4-fold) increase in influenza-antibody titers for ≥2/4 strains) at 30 days post-vaccination and changes in sNfL levels.ResultsAll patients treated with DMF fulfilled the responder criteria for immunization compared with 53% of the controls. However, higher proportions of HCs already had influenza-antibody titers ≥1:40 at baseline (53% vs. 41%, p = 0.174). sNfL levels were comparable among both groups at baseline and did not increase 34 days after vaccination. In addition, no clinical or radiological disease reactivation was found.ConclusionDMF-treated patients mount an adequate humoral immune response to influenza vaccines. Within the limits of the small cohort investigated, our data suggest that influenza immunization is not associated with clinical or subclinical disease reactivation.

Background: Serum neurofilament light chain levels (sNfL) and impairment of olfactory function emerge as biomarkers in multiple sclerosis (MS). However, the relation between sNfL and olfactory function in MS has not been investigated yet. Objective: We aimed to determine whether sNfL levels correlate with olfactory function in relapsingremitting (RR) MS. Methods: We annually measured sNfL and olfactory function (Sniffin' Sticks test: Threshold (T) and combined discrimination-identification (DI) score) in 80 RRMS patients and compared sNfL to T and DI scores. Results: T scores significantly correlated with sNfL levels at simultaneous measurement (-1.5 points, 95% CI: -2.6-0.5 per 10 pg/ml sNfL increase; p < 0.001 per 10 pg/ml sNfL increase), but not at temporally distant measurement. Patients with 2 sNfL measures above the 75th percentile displayed significantly larger DI decrease (median 3.0 points, IQR 2.0-4.5) compared to patients with no or only one sNfL measure above the 75th percentile (0.0, IQR -0.5-0.5, p < 0.001 and 1.0, IQR 0.0-3.30, p ¼ 0.008, respectively). 13-18% of the variance in T and 22% in DI decrease could be predicted from sNfL levels. Conclusions: sNfL correlates with different qualities of olfactory function in patients with RRMS further strengthening the value of olfactory function as a biomarker of inflammation and axonal damage in MS.