Blood test may detect earliest signs of Alzheimer's disease.

A Harvard-affiliated study followed 317 older adults and found that higher or rising blood pTau217 levels were associated with faster accumulation of Alzheimer's pathology and often increased before amyloid PET scans became positive.

A Harvard-affiliated team at Mass General Brigham reports that blood levels of phosphorylated tau 217 (pTau217) were linked to later development of Alzheimer's disease pathology. The study tracked 317 cognitively healthy adults, aged about 50 to 90, over an average of eight years. Participants had repeated blood tests for pTau217, PET scans for amyloid and tau, and long-term cognitive testing. The results were published in Nature Communications. Key findings: - Higher baseline or increasing plasma pTau217 predicted a faster buildup of Alzheimer's-related pathology. - Increases in pTau217 frequently occurred before amyloid PET scans became positive. - Participants with low pTau217 at the start were unlikely to develop substantial amyloid accumulation on PET over several years. Summary: The study indicates that pTau217 measured in blood can show early biological changes associated with Alzheimer's disease, sometimes preceding changes seen on amyloid PET scans. The authors say it is too early to recommend routine clinical testing, but they report the marker may be useful for screening participants in prevention trials while further research clarifies clinical use.