MAPT and amyloidosis: In particular, the levels of Aβ (determined by Aβ-42/40 ratio) and tau proteins (phosphorylated tau at threonine residues 217 and 181 and total tau) quantified in blood (4–6) and cerebrospinal fluid (CSF) (7–9) using biochemical assays (10) serve as indicators of amyloid and tau pathology.