Nat Commun
Blood biomarker flags Alzheimer’s risk years before scans or symptoms
Clinical Takeaway: In cognitively unimpaired older adults, rising plasma pTau217 levels may signal preclinical Alzheimer’s risk long before amyloid PET scans turn positive, while very low levels suggest minimal near-term risk.
Alzheimer’s pathology begins decades before symptoms; identifying high- and low-risk patients earlier could transform prevention trials and future clinical care.
A simple blood test may reveal Alzheimer’s disease risk years earlier than previously possible. In this longitudinal study, researchers tracked plasma phosphorylated tau 217 (pTau217) alongside brain imaging and cognition in 317 cognitively unimpaired adults aged 50 to 90 years from the Harvard Aging Brain Study, followed for a mean of 8 years.
Individuals with higher baseline pTau217 showed significantly faster accumulation of amyloid-β and tau on PET imaging and greater subsequent cognitive decline. Notably, increases in pTau217 often occurred before amyloid PET scans became positive, suggesting this blood biomarker detects disease activity at an even earlier stage. Participants with very low pTau217 levels at baseline were unlikely to develop meaningful amyloid buildup or cognitive decline over years of follow-up.
“We used to think that PET scans revealed the earliest signs of Alzheimer’s progression,” said lead author Hyun-Sik Yang, MD. “But now we’re seeing that pTau217 can be detected years earlier, well before clear abnormalities appear on amyloid PET scans.”
Authors say longitudinal pTau217 testing could help identify candidates for prevention trials and, eventually, guide earlier intervention strategies.
Source: Yang HS, et al. (2026, April 14). Nat Commun. Plasma phosphorylated tau 217 and longitudinal trajectories of Aβ, tau, and cognition in cognitively unimpaired older adults