GFAP and tauopathy: Plasma Aβ42/40 ratio levels decrease in the blood plasma as deposition increases in the brain, whereas increasing plasma neurofilament light (NfL), phosphorylated tau (p‐tau) 181 and 231, and glial fibrillary acidic protein (GFAP) concentrations occurring later provide useful measures of neurodegeneration, tauopathy, and neuroinflammation.3, 24, 25, 26