MAPT and Alzheimer disease: The table also includes classical AD biomarkers used in clinical CSF and blood tests such as Aβ42, MAPT (total tau and phosphorylated tau at sites 181, 205, 217, or 231), NFL, and GFAP, as well as relevant protein ratios (e.g., Aβ42/Aβ40 and pTau-217/Aβ42).