Blood biomarkers for predicting disability worsening in progressive multiple sclerosis: A multinational, individual participant-level analysis

Background and objectives: Biologically informative markers like glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) may help predict confirmed disability worsening (CDW) in multiple sclerosis (MS). However, data on the prognostic value of their blood concentrations in progressive MS (PMS) are limited, and there are substantial discrepancies in the published literature. This international collaboration uses individual participant data to define the prognostic value of serum GFAP and NfL in people with PMS (pwPMS). Methods: Data were collected from BioMS-eu network centres and collaborating cohorts. pwPMS with primary progressive MS (PPMS) or secondary progressive MS (SPMS) with at least one GFAP value and at least three follow-up expanded disability status scale (EDSS) scores were included. The prognostic value of serum GFAP and NfL age- and sex-adjusted Z-scores for future CDW was evaluated using Cox regression models, accounting for sex, age, baseline disease duration and EDSS, and dominant treatment during follow-up. Results: 1058 participants and 7530 encounters were included (median age 53 years (IQR: 44 to 59), 57% female, follow-up 4.6 years (2.9 to 8.4)) with median baseline GFAP of 0.74 (-0.10 to 1.55) and NfL of 0.64 (-0.36 to 1.51). 723 CDW events were recorded. Each GFAP Z-score increase was associated with ∼10% higher CDW risk (adjusted HR (aHR) 1.107 (1.001 to 1.225), p=0.049). Results were mainly driven by SPMS participants (n=613, aHR 1.242 (1.073 to 1.438), p=0.004). Higher NfL Z-scores predicted CDW only in PPMS participants (1.236 (1.092 to 1.399), p=0.001). Conclusions: GFAP was a prognostic indicator for future CDW in pwPMS, especially in pwSPMS. On the other hand, NfL was predictive of CDW only in pwPPMS.