NEFL and nervous system disorder: NfL is the most abundant and soluble Nf subunit and can be released into blood and CSF in diverse neurological diseases reflecting neuroaxonal injury (Petzold, 2005; Lu et al., 2015; Mattsson et al., 2017; Khalil et al., 2018; Steinacker et al., 2018; Verde et al., 2019).