MAPT and amyotrophic lateral sclerosis: In the future, development of a highly sensitive, multiplexed MSD assay to measure cryptic HDGFL2 and other disease-relevant markers simultaneously, such as pNfH, NfL, tau, amyloid-β and α-synuclein, would provide additional insight into disease staging for ALS and other neurodegenerative diseases exhibiting TDP-43 pathology.