BACKGROUND: There is a lack of reliable biomarkers of axonal degeneration. 
Neurofilaments are promising candidates to fulfil this task. We compared two 
highly sensitive assays to measure two subunits of the neurofilament protein 
(neurofilament light (NfL) and neurofilament heavy chain (NfH)).
METHODS: We evaluated the analytical and clinical performance of the 
UmanDiagnostics NF-light(®) enzyme-linked immunosorbent assay (ELISA) in the 
cerebrospinal fluid (CSF) of a group of 148 patients with clinically isolated 
syndrome (CIS) or multiple sclerosis (MS), and 72 controls. We compared our 
results with referring levels of our previously-developed CSF NfH(SMI35) assay.
RESULTS: Exposure to room temperature (up to 8 days) or repetitive thawing (up 
to 4 thaws) did not influence measurement of NfL concentrations. Values of NfL 
were higher in all disease stages of CIS/MS, in comparison to controls (p ≤ 
0.001). NfL levels correlated with the Expanded Disability Status Scale (EDSS) 
score in patients with relapsing disease (r(s) = 0.31; p = 0.002), spinal cord 
relapses and with CSF markers of acute inflammation. The ability of NfL to 
distinguish patients from controls was greater than that of NfH(SMI35) in both 
CIS patients (p = 0.001) and all MS stages grouped together (p = 0.035).
CONCLUSIONS: NfL proved to be a stable protein, an important prerequisite for a 
reliable biomarker, and the NF-light(®) ELISA performed better in discriminating 
patients from controls, compared with the ECL-NfH(SMI35) immunoassay. We 
confirmed and expanded upon previous findings regarding neurofilaments as 
quantitative markers of neurodegeneration. Our results further support the role 
of neurofilaments as a potential surrogate measure for neuroprotective treatment 
in MS studies.