MAPT and Alzheimer disease: The main laboratory tests used to identify AD patients are Aβ40, Aβ42, the Aβ42/Aβ40 ratio, phosphorylated Tau 181 (pTau181), phosphorylated Tau 217 (pTau181), phosphorylated Tau 231 (pTau217) and total Tau (tTau).