MAPT and Alzheimer disease: T-tau levels in PSP (median 429 ng/mL) were significantly different from Alzheimer's disease subjects (median 840 ng/mL) but not healthy controls, PD or multiple system atrophy subjects (median levels of 473, 371 and 528 ng/mL, respectively).42 When studied longitudinally in PSP participants, Boxer et al.46 and Bäckström et al.47 found no changes in either CSF p-tau181 or t-tau over a 1-year period (Supplementary Table 1).