MAPT and Alzheimer disease: Using SIMOA and xMAP technology, Aβ42, which positively correlated with CSF Aβ42 but negatively with CSF t-tau, was higher in the MCI stage than in the AD stage, while t-tau was positively associated with the burden of brain tau deposition on tau PET across the AD spectrum, that is, Aβ42 elevates during the MCI stage and reaches a plateau before the demented stage, while t-tau increases with AD–associated tau pathology15,43.