A blood test could help predict Alzheimer’s symptom onset, with researchers reporting estimates accurate to within three to four years.
The method uses levels of a protein called p-tau217, measured in plasma, the liquid part of blood, to estimate the age at which symptoms are likely to appear.
P-tau217 reflects the build-up of amyloid and tau, misfolded proteins linked to Alzheimer’s that can accumulate in the brain many years before symptoms emerge.
The findings could support the design of preventive clinical trials and, over time, help identify people most likely to benefit from early intervention.
Kellen K. Petersen, an instructor in neurology at Washington University School of Medicine in St. Louis and the study’s lead author, said: “It turns out that amyloid and tau also accumulate in a consistent pattern and the age they become positive strongly predicts when someone is going to develop Alzheimer’s symptoms.
“We found this is also true of plasma p-tau217, which reflects both amyloid and tau levels.
“These clock models could make clinical trials more efficient by identifying individuals who are likely to develop symptoms within a certain period of time.
“With further refinement, these methodologies have the potential to predict symptom onset accurately enough that we could use it in individual clinical care.”
The study analysed data from 603 older adults living independently in the community, drawn from two long-running Alzheimer’s research programmes.
Researchers found that the age at which p-tau217 levels become elevated strongly predicts when symptoms will develop.
Older participants typically progressed from raised p-tau217 to symptoms more quickly than younger individuals, suggesting younger brains may be more resilient to neurodegeneration.
For example, a person with elevated p-tau217 at age 60 developed symptoms 20 years later, while someone whose levels rose at age 80 developed symptoms 11 years later.
Suzanne E. Schindler, associate professor in the university’s department of neurology and the study’s senior author, said: “Our work shows the feasibility of using blood tests, which are substantially cheaper and more accessible than brain imaging scans or spinal fluid tests, for predicting the onset of Alzheimer’s symptoms.”
She added: “In the near term, these models will accelerate our research and clinical trials.
“Eventually, the goal is to be able to tell individual patients when they are likely to develop symptoms, which will help them and their doctors to develop a plan to prevent or slow symptoms.”
The team also found that the predictive model worked with multiple p-tau217-based diagnostic tests, suggesting the approach is robust.
The authors have shared their code so other researchers can further refine the models.
