Serum neurofilament light chain levels are increased in patients with a clinically isolated syndrome

Background Neurofilament light chain (NfL) represents a promising biomarker for axonal injury. We present the first exploratory study on serum NfL in patients with a clinically isolated syndrome (CIS) and healthy controls. Methods We investigated serum NfL levels in 100 patients with CIS with a short conversion interval to clinically definite multiple sclerosis (MS) (fast converters (FC), median (IQR) conversion time: 110 days (79-139)); 98 patients with non-converting CIS (non-converters (NC), follow-up: 6.5 years (5.3-7.9)); and 92 healthy controls. Results NfL levels were higher in FC (24.1 pg/mL (13.5-51.8)) and NC (19.3 pg/mL (13.6-35.2)) than in healthy controls (7.9 pg/mL (5.6-17.2)) (OR=5.85; 95% CI 2.63 to 13.02; p=1.5×10^-5 and OR=7.03; 95% CI 2.85 to 17.34; p=2.3×10^-5, respectively). When grouping FC and NC, increased serum NfL concentration was also associated with increasing numbers of T2 hyperintense MRI lesions (OR=2.36; 95% CI 1.21 to 4.59; p=0.011), gadolinium-enhancing lesions (OR=2.69; 95% CI 1.13 to 6.41; p=0.026) and higher disability scores (OR=2.54; 95% CI 1.21 to 5.31; p=0.013) at CIS diagnosis. Conclusions If replicated in future studies, serum NfL may represent a reliable and easily accessible biomarker of early axonal damage in CIS and MS.