Serum Glial Fibrillary Acidic Protein Compared With Neurofilament Light Chain as a Biomarker for Disease Progression in Multiple Sclerosis
Authors: Meier Stephanie , Willemse Eline A.J. , Schaedelin Sabine , Oechtering Johanna , Lorscheider Johannes , Melie-Garcia Lester , Cagol Alessandro , Barakovic Muhamed , Galbusera Riccardo , Subramaniam Suvitha , Barro Christian , Abdelhak Ahmed , Thebault Simon , Achtnichts Lutz , Lalive Patrice , Müller Stefanie , Pot Caroline , Salmen Anke , Disanto Giulio , Zecca Chiara , D’Souza Marcus , Orleth Annette , Khalil Michael , Buchmann Arabella , Du Pasquier Renaud , Yaldizli Özgür , Derfuss Tobias , Berger Klaus , Hermesdorf Marco , Wiendl Heinz , Piehl Fredrik , Battaglini Marco , Fischer Urs , Kappos Ludwig , Gobbi Claudio , Granziera Cristina , Bridel Claire , Leppert David , Maleska Maceski Aleksandra , Benkert Pascal , Kuhle Jens 
Published: February 2023

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 &amp;lt; .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 &amp;lt; .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 &amp;lt; .001) and PIRA (HR, 4.71; 95% CI, 2.05-9.77; P &amp;lt; .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.