Blood Tests Offer New Hope for Alzheimer’s Detection in Down Syndrome

Individuals with Down syndrome face one of the highest risks of developing Alzheimer’s disease. However, they have often been excluded from recent advancements in blood tests designed to detect this condition. A new study highlights a potential shift. The research indicates that two existing blood tests can identify Alzheimer’s-related changes in people with Down syndrome almost as accurately as in the general population. These findings, published in Communications Medicine, might simplify the Alzheimer’s screening process for this group by reducing the need for invasive procedures.

Blood Tests Show Promise for Down Syndrome Patients

The study examined two tests—Lumipulse G p-tau217/β-Amyloid 1-42 and PrecivityAD2. These tests search for signs of amyloid buildup and abnormal tau proteins in the brain, both closely tied to Alzheimer’s. While blood tests are gaining popularity due to their simplicity compared to brain scans or spinal taps, individuals with Down syndrome have typically been left out of related studies. According to Michael Rafii, a clinical neurology professor at the Keck School of Medicine of USC, these blood tests are transforming the field. Exclusion of people with Down syndrome is notable as they are at a very high risk of Alzheimer’s. By age 40, nearly all people with Down syndrome have amyloid plaques in their brains. Even though not everyone with these plaques develops Alzheimer’s dementia, the lifetime risk exceeds 90%. This connection arises from genetic duplications that cause Down syndrome and result in increased amyloid accumulation, a hallmark of Alzheimer’s.

Challenges in Diagnosing Alzheimer’s in Down Syndrome

Diagnosing Alzheimer’s in this group is notably challenging. Dr. Yıldız Değirmenci of Medicana Health Group, not involved in the study, explains the difficulty lies in distinguishing new cognitive decline from intellectual disabilities present since childhood. The disease often appears differently, with early changes in executive function, personality, or behavior, diverging from the memory loss typical in late-onset Alzheimer’s. The study recruited 39 participants with Down syndrome, who underwent blood tests and PET scans, regarded as the gold standard for detecting Alzheimer’s. The results showed that the blood tests effectively identified abnormal amyloid levels in the brain. Researchers also developed preliminary thresholds to distinguish between individuals with and without Alzheimer’s-related pathology in the Down syndrome population.

In practical terms, these findings suggest that a simple blood test could indicate the likelihood of Alzheimer’s before conducting more complex tests. This accessibility is crucial as current diagnostics, such as amyloid PET scans and lumbar punctures, are often limited to specialized centers. Zinayida Schlachetzki, the study’s first author, notes that blood tests are more accessible, cost-effective, and less burdensome for patients. Dr. Değirmenci supports the potential of blood-based biomarkers for expanding diagnosis access but cautions they should be interpreted with clinical history and cognitive assessments, not in isolation.

Next Steps for Blood Testing

Beyond identifying Alzheimer’s, these tests might help rule out the disease to explore other causes of symptoms like memory issues or behavioral changes. According to the study’s authors, eliminating Alzheimer’s from the list of possibilities helps doctors focus on other explanations, such as depression or sleep apnea. However, further research is needed before widespread adoption. Researchers aim to test the diagnostic thresholds on a larger group, confirming how they should be used alongside cognitive and behavioral assessments. Michael S. Rafii notes that the primary barrier to routine use with Down syndrome individuals is validation, requiring larger, diverse, and long-term studies. Other challenges include regulatory approval, insurance coverage, lab availability, clinician education, and equitable access to treatment. Counseling must accompany testing, as Alzheimer’s-related changes can be detected long before dementia symptoms.

Despite these hurdles, the study has set the stage for future investigations. Blood-based screening will help identify participants for a clinical trial on the Alzheimer’s treatment donanemab for people with Down syndrome. The research also addresses inclusion. While they have significantly contributed to understanding Alzheimer’s biology, people with Down syndrome have often been excluded from trials. Rafii stresses the importance of including this group in research, noting that they have influenced much of the existing knowledge on Alzheimer’s.

Other contributors to the study include Oliver Langford, Michael Donohue, Xiaoyu Zhou, Sonal Sukreet, Sara Abdel-Latif, and Robert Rissman from USC; Matthew Zammit from the University of Wisconsin–Madison; and Joel Braunstein from C2N Diagnostics. The study was funded by the National Institutes of Health [R61AG066543]. DOI: 10.1038/s43856-026-01709-0