NEFL and necrotizing vasculitis: However, serum neurofilament light (NFL), a structural protein specific to neurons that was previously proven indicative of axonal damage in central nervous system disorders such as multiple sclerosis, has displayed a 100% specificity and 82% sensitivity for a cut-off value of 155 pg/ml in discriminating between active vasculitic neuropathy and non-vasculitic neuropathy or systemic vasculitis without neuropathy (Bischof et al., 2018).