Researchers analyzed 1,707 older adults from the A4/LEARN studies to compare plasma p-tau217 and tau PET as markers of disease progression in preclinical Alzheimer's disease. Tau PET accumulation—especially in frontoparietal regions—strongly correlated with concurrent cognitive decline (ρ up to −0.68), making it a powerful real-time tracker. Plasma p-tau217 was most valuable as a baseline predictor of future cognitive decline (ρ=−0.47) and for efficient participant selection in trials. Notably, plasma p-tau217 changes did not correlate with concurrent cognitive changes in the tau PET substudy, though a modest association appeared in the larger full plasma cohort. The findings suggest tau PET and plasma p-tau217 serve complementary but distinct roles in Alzheimer's trial design.
