NEFL and brain injury: GFAP, an intermediate filament, maintains astrocyte structural integrity, while UCH-L1 is a cellular enzyme essential for neuronal homeostasis.10,11 Together, GFAP and UCH-L1 have demonstrated strong diagnostic utility in differentiating individuals with concussions or mild traumatic brain injury (TBI) from healthy controls with 100% sensitivity and 67% specificity12–14 and in identifying patients with intracranial bleeding.15 Tau and NfL are key structural proteins within neuronal axons, contributing to microtubules and neurofilaments.