Relapse or no relapse in multiple sclerosis: Can disease activity biomarkers support the clinician?

Background In relapsing-remitting multiple sclerosis (RRMS), the assessment of clinical disease activity can be challenging. Objectives To determine the diagnostic potential of serum neurofilament light (sNfL) and glial fibrillary acidic protein (sGFAP) to distinguish a relapse from other causes of deterioration. Methods In this multicenter, prospective study, RRMS patients with new neurological symptoms in the last 14 days were followed for 12 weeks. A diagnosis was established by the treating physician or, when in doubt, a panel of experienced neurologists. Blood samples were taken at baseline and week 12. Results A total of 65 patients were included. At baseline, patients with a clear relapse had a significantly higher median sNfL (14.6 pg/mL) than those with a clear other cause (9.5 pg/mL, p = 0.004). Although not significant after correction for multiple testing, median sGFAP was also higher in relapse patients (73.0 vs 64.6 pg/mL, p = 0.036). An sNfL value below 6.0 pg/mL had a high sensitivity (67% at baseline (CI 22.3–95.7%) and 100% at follow-up (CI 54.1–100%)) to rule out a relapse. Conclusions Analysis of sNfL level can be useful as an add-on investigation to determine whether disease activity is present in patients with RRMS presenting with new symptoms.