Simple blood test can forecast Alzheimer’s years before memory loss

In a study published Feb. 19 in Nature Medicine, the team reported that their model could forecast the onset of Alzheimer’s symptoms within about three to four years. Such accuracy could help researchers design faster and more targeted clinical trials for treatments aimed at preventing the disease. Over time, it may also help identify people who are most likely to benefit from early intervention.

More than 7 million Americans are living with Alzheimer’s. The Alzheimer’s Association estimates that the cost of caring for people with Alzheimer’s and other dementias will reach nearly $400 billion in 2025. Although there is still no cure, tools that can anticipate when symptoms might begin could support efforts to delay or reduce their impact.

“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,” said senior author Suzanne E. Schindler, MD, PhD, an associate professor in the WashU Medicine Department of Neurology. She explained that these models could shorten the time needed to evaluate potential preventive therapies.

“In the near term, these models will accelerate our research and clinical trials,” she said. “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 Role of the p tau217 Blood Biomarker

The research was conducted as part of a project organized by the Foundation for the National Institutes of Health Biomarkers Consortium, a public private partnership that includes WashU Medicine.

The predictive approach centers on measuring p tau217, a protein found in plasma, the liquid component of blood. By analyzing levels of this protein, the researchers estimated the age at which someone may begin experiencing Alzheimer’s symptoms. Today, p tau217 testing can help doctors diagnose Alzheimer’s in patients who already have cognitive impairment. However, these tests are not recommended for people without symptoms outside of research studies or clinical trials.

To better understand how long it typically takes for symptoms to appear after p tau217 levels rise, Schindler and lead author Kellen K. Petersen, PhD, an instructor in neurology at WashU Medicine, examined data from 603 older adults living independently. Participants were enrolled in two long running studies: the WashU Medicine Knight Alzheimer Disease Research Center (Knight ADRC) and the Alzheimer’s Disease Neuroimaging Initiative (ADNI), which includes multiple research sites across the U.S.

Testing Across Multiple Platforms

In the Knight ADRC group, plasma p tau217 was measured using PrecivityAD2, a clinically available Alzheimer’s blood test developed by C2N Diagnostics. C2N is a WashU startup co founded by WashU Medicine researchers David M. Holtzman, MD, the Barbara Burton and Reuben M. Morriss III Distinguished Professor, and Randall J. Bateman, MD, the Charles F. & Joanne Knight Distinguished Professor of Neurology. Both are coauthors of the study. In the ADNI group, p tau217 levels were measured using tests from other companies, including one cleared by the U.S. Food and Drug Administration.

Earlier research has shown that plasma p tau217 closely reflects the buildup of amyloid and tau in the brain, as seen on PET scans. Amyloid and tau are abnormal proteins that accumulate gradually and are considered defining features of Alzheimer’s disease. They can begin building up many years before memory problems emerge.

“Amyloid and tau levels are similar to tree rings — if we know how many rings a tree has, we know how many years old it is,” Petersen 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.”

Predicting Symptom Timing Within a Few Years

The researchers found that their model could estimate the age at which symptoms would begin within a margin of about three to four years. Age also influenced how quickly symptoms followed rising p tau217 levels. Older adults tended to develop symptoms sooner after the protein became elevated compared with younger individuals. This pattern suggests that younger brains may tolerate disease related changes longer, while older adults may show symptoms at lower levels of underlying pathology.

For instance, a person whose p tau217 levels increased at age 60 developed symptoms roughly 20 years later. In contrast, if levels first rose at age 80, symptoms typically appeared about 11 years later.

The model performed well across other p tau217 based diagnostic tests beyond PrecivityAD2, supporting its reliability and broader applicability.

To encourage further research, the team made their model development code publicly available. Petersen also created a web-based application that allows researchers to explore the clock models in greater detail.

“These clock models could make clinical trials more efficient by identifying individuals who are likely to develop symptoms within a certain period of time,” Petersen said. “With further refinement, these methodologies have the potential to predict symptom onset accurately enough that we could use it in individual clinical care.”

He added that other blood biomarkers are linked to cognitive decline in Alzheimer’s disease, and combining additional markers in future studies could further improve predictions of when symptoms will begin.

Petersen KK, Milà-Alomà M, Li Y, Du L, Xiong C, Tosun D, Saef B, Saad ZS, Du-Cuny L, Coomaraswamy J, Mordashova Y, Rubel CE, Meyers EA, Shaw LM, Dage JL, Ashton NJ, Zetterberg H, Ferber K, Triana-Baltzer G, Baratta M, Rosenbaugh EG, Cruchaga C, McDade E, Holtzman DM, Morris JC, Sabandal JM, Bateman RJ, Bannon AW, Potter WZ, Schindler SE. Predicting onset of symptomatic Alzheimer disease with a plasma %p-tau217 clock. Nature Medicine. Feb. 19, 2026. DOI: 10.1038/s41591-026-04206-y

The findings are part of the Foundation for the National Institutes of Health (FNIH) Biomarkers Consortium “Biomarkers Consortium, Plasma Aβ and Phosphorylated Tau as Predictors of Amyloid and Tau Positivity in Alzheimer’s Disease” Project. The work was supported by scientific and financial contributions from industry, academic, patient advocacy, and government partners. Funding partners included AbbVie Inc., Alzheimer’s Association®, Diagnostics Accelerator at the Alzheimer’s Drug Discovery Foundation, Biogen, Janssen Research & Development, LLC, and Takeda Pharmaceutical Company Limited. Private sector funding was managed by the Foundation for the National Institutes of Health.

The Biomarkers Consortium, Plasma Aβ and Phosphorylated Tau as Predictors of Amyloid and Tau Positivity in Alzheimer’s Disease Project was carried out through a public private partnership managed by the Foundation for the National Institute of Health (FNIH) and funded by AbbVie Inc., Alzheimer’s Association®, Diagnostics Accelerator at the Alzheimer’s Drug Discovery Foundation, Biogen, Janssen Research & Development, LLC, and Takeda Pharmaceutical Company Limited. Statistical analyses were supported by National Institute on Aging grant R01AG070941.

Data used in preparation of this article were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database (adni.loni.usc.edu). As such, the investigators within the ADNI contributed to the design and implementation of ADNI and or provided data but did not participate in analysis or writing of this report.