NEFL and amyotrophic lateral sclerosis: To confirm that the expression and regulation of ALS-relevant proteins identified in our plasma proteomic study could be reproduced using an orthogonal technique of immunodetection, plasma levels of three well-known ALS proteins (Fig. S5 Supplemental Data) i.e. neurofilament light and heavy (NfL, NfH) polypeptides and apolipoprotein E (ApoE; Fig. S5 Supplemental Data) were tested.