GFAP and multiple sclerosis: The emergence of the single molecule arrays (SIMOA), an ultra-sensitive enzyme-linked immunosorbent assay (ELISA) technique, for measuring NfL and GFAP levels in peripheral blood has led to the renaissance of NfL and GFAP as biomarkers in several diseases characterized by axonal loss in the central nervous system and peripheral nervous system, including multiple sclerosis, stroke, head injury, dementia, and immune-mediated neuropathy9,11.