People with Down syndrome encounter one of the highest risks of developing Alzheimer’s disease. However, they have largely been overlooked in recent advancements in Alzheimer’s blood tests. A new study indicates this situation might be starting to change.
Researchers discovered two existing blood tests could identify Alzheimer’s-related changes in individuals with Down syndrome. They showed nearly the same accuracy as in the general population. Published in Communications Medicine, the study could be pivotal for making Alzheimer’s screening more accessible for those who depend on invasive testing.
Blood Tests Show Promise for Down Syndrome Patients
Two tests, Lumipulse G p-tau217/β-Amyloid 1-42 and PrecivityAD2, focus on detecting signs of amyloid accumulation and abnormal tau proteins. These markers are closely associated with Alzheimer’s disease and change years before significant symptoms appear.
Though blood tests present a simpler option compared to brain scans or spinal taps, people with Down syndrome often aren’t included in test evaluations. Professor Michael Rafii from the Keck School of Medicine of USC highlighted that the exclusion is concerning due to the extraordinarily high risk of Alzheimer’s in this community.
Almost all individuals with Down syndrome have amyloid plaques in their brains by age 40. Although not everyone develops Alzheimer’s dementia, the lifetime risk exceeds 90 percent. This link is attributed to genetic changes that cause Down syndrome, which also lead to increased amyloid buildup, a key aspect of Alzheimer’s.
Challenges in Diagnosing Alzheimer’s in People With Down Syndrome
Dr. Yıldız Değirmenci from Medicana Health Group explained that diagnosing Alzheimer’s in people with Down syndrome entails distinguishing new cognitive issues from lifelong intellectual disabilities. The disease can present differently in this group, showing early changes in executive functioning, personality, or behavior, rather than the memory loss seen in late-onset Alzheimer’s.
The study involved 39 participants with Down syndrome, who underwent both blood testing and PET scans, a standard for detecting Alzheimer’s-related changes. Blood tests identified those with abnormal amyloid levels, and researchers proposed preliminary thresholds for Alzheimer’s-related pathology within the Down syndrome population.
In practical terms, these findings suggest potential for simpler preliminary Alzheimer’s screening via blood tests before more complex diagnostics. Currently, options like amyloid PET scans are only available in larger medical centers, and lumbar punctures are invasive.
Zinayida Schlachetzki, the study’s first author, pointed out the accessibility of blood tests compared to other methods. They are easier to perform, less expensive, and scalable.
Next Steps for Blood Testing
Beyond detecting Alzheimer’s, these tests could aid in understanding other causes of symptoms like memory issues or behavioral changes. With reliable tools to rule out Alzheimer’s, doctors can explore other reasons for symptoms.
Michael S. Rafii emphasized the need for further validation before routine use in people with Down syndrome. He mentioned hurdles such as regulatory reviews, insurance coverage, and access to specialists.
The team’s encouraging results are expected to impact future research. They will incorporate blood-based screening in a clinical trial for Alzheimer’s treatment donanemab in people with Down syndrome.
This study also focuses on inclusion, aiming to correct the exclusion of Down syndrome individuals from clinical trials, despite their contributions to Alzheimer’s research.
“Being inclusive of this group is not only a scientific imperative, but also an ethical one,” Rafii said. “This population taught us so much about the biology of Alzheimer’s. It’s sad, and wrong, to see them excluded from clinical trials.”
Other co-authors are Oliver Langford, Michael Donohue, Xiaoyu Zhou, Sonal Sukreet, Sara Abdel-Latif and Robert Rissman of USC; Matthew Zammit of the University of Wisconsin–Madison; Joel Braunstein of C2N Diagnostics. The study is supported by the National Institutes of Health [R61AG066543].
DOI: 10.1038/s43856-026-01709-0
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