Neurofilament light chain levels in patients with antibodies to myelin oligodendrocyte glycoprotein (MOG-Abs)

Objective: to assess neurofilament light chain (NfL) concentration in MOG-Ab-positive patients according to clinical/paraclinical characteristics and to evaluate intraindividual changes over time. Background: NfL is a marker of axonal injury, increased in serum/CSF of patients with several neurological disorders in correlation with clinical and radiological activity. As a consequence, NfL could be a useful biomarker to monitor disease activity in MOG-Ab-related inflammatory conditions, where the course is highly heterogeneous and unpredictable. Design/methods: sera and available (n=17) CSF samples of 63 consecutive MOG-Ab-positive patients tested at the Neuropathology Laboratory, University of Verona, between March 2015-August 2019 using a live cell-based assay were analysed for NfL using SIMOA Nf-light kit (SR-X analyser). Sixty follow-up samples of 28 patients were also analysed. Clinical and radiological data at sampling and at last follow-up were collected in each case. Results: we observed a moderate correlation between serum NfL values and age at sampling, with higher levels detected in older subjects (rs=0.41, p < 0.001). In addition, a moderate correlation was noted between paired serum/CSF NfL values (rs=0.42, p =0.09), but not between serum MOG-Ab titer and serum NfL levels (rs=0.15, p = 0.11). CSF only MOG-Ab positive cases had higher CSF NfL levels in comparison with seropositive ones. Interestingly, NfL values correlated with disability at sampling (rs=0.43, p < 0.001) but did not differentiate monophasic and relapsing cases. When analyzing follow-up samples, NfL levels decreased (n=30) or remain stable (n=23) in comparison with first measurement in most cases, including those on relapse, in parallel with a decrease of clinical disability in comparison with first event EDSS. Finally, although radiologically and clinically active patients tend to have higher NfL values in comparison with inactive ones, the difference between the groups was not significant. Conclusions: The role of serum NfL as a potential biomarker of neurological disability in MOG-Ab positive patients needs further clarification in in prospective studies.