Blood Tests Offer New Hope for Down Syndrome and Alzheimer’s Diagnosis

People with Down syndrome face a high risk of Alzheimer’s disease. Historically, they have been overlooked in blood test developments for this condition. A recent study indicates a shift. Researchers have found two blood tests, currently used to detect Alzheimer’s biomarkers, are nearly as effective in individuals with Down syndrome as in the general population. Findings published in Communications Medicine could simplify Alzheimer’s screening, which typically relies on invasive testing for this group.

Blood Tests and Alzheimer’s Detection

Scientists focused on two tests: Lumipulse G p-tau217/β-Amyloid 1-42 and PrecivityAD2. These detect amyloid buildup and abnormal tau proteins, both linked to Alzheimer’s. They start altering long before symptoms become severe. While blood tests offer simplicity compared to brain scans or spinal taps, those with Down syndrome have not been included in these studies historically.

Michael Rafii, professor of clinical neurology at USC, highlights how blood tests are transforming Alzheimer’s field. This exclusion is significant, as amyloid plaques almost always develop in the brains of people with Down syndrome by age 40. Although not every individual develops dementia, the lifetime risk remains high. The genetic changes associated with Down syndrome contribute to increased amyloid accumulation.

Challenges in Diagnosing Alzheimer’s in Down Syndrome

According to Dr. Yıldız Değirmenci, diagnosing Alzheimer’s in individuals with Down syndrome is challenging. Clinicians must distinguish between new cognitive decline and lifelong intellectual disabilities. The disease often manifests differently in this group, with early changes in personality, behavior, or executive functioning, instead of the memory loss seen in late-onset Alzheimer’s.

The study enrolled 39 people with Down syndrome, conducting both blood testing and PET scans. Blood tests identified individuals with abnormal amyloid levels, achieving success. Researchers are developing preliminary thresholds to differentiate between those with and without Alzheimer’s-related brain changes.

Zinayida Schlachetzki, the study’s first author, emphasized accessibility. Blood tests are easier, less expensive, scalable, and less burdensome than other methods. Değirmenci agrees, underscoring the benefits of blood-based biomarkers but cautioning that they should complement clinical history and cognitive assessments.

Future of Blood Testing

The study suggests additional benefits beyond Alzheimer’s identification. Symptoms such as memory issues or behavioral changes have many causes. A reliable exclusion method for Alzheimer’s can help pinpoint other reasons.

Rafii notes that excluding Alzheimer’s is valuable for families, allowing doctors to seek other causes, like untreated depression or sleep apnea. However, he stresses more extensive research is needed for broader application. Larger, diverse cohorts are required to establish proper diagnostic thresholds.

Key barriers to routine implementation include validation, regulatory review, insurance, laboratory availability, and clinician education. Testing should include counseling, as biological changes precede dementia symptoms.

The study influences future research, with blood-based screening identifying potential participants for trials, like testing donanemab for Alzheimer’s in people with Down syndrome. Rafii emphasizes the need for inclusion, as they’ve contributed significantly to understanding Alzheimer’s biology.

Inclusion in clinical trials and studies is both a scientific and ethical necessity; people with Down syndrome have advanced knowledge of the biology of Alzheimer’s.

Reference: Other study co-authors include Oliver Langford, Michael Donohue, Xiaoyu Zhou, Sonal Sukreet, Sara Abdel-Latif, Robert Rissman, Matthew Zammit, and Joel Braunstein.

Supported by the National Institutes of Health [R61AG066543]. DOI: 10.1038/s43856-026-01709-0