Blood Tests Detect Alzheimer’s in People With Down Syndrome, Study Finds

New blood tests are beginning to reshape Alzheimer’s diagnostics by detecting molecular changes linked to the disease years earlier than symptom onset. Compared with brain imaging or lumbar puncture, these assays are less invasive and easier to scale, offering a practical route to earlier intervention. Early identification matters because disease-modifying therapies may have greater impact before extensive neurodegeneration becomes established.

But one high-risk population remains systematically overlooked in many testing advances: people with Down syndrome. Alzheimer’s incidence is dramatically higher in this group, yet key biomarker assays often lack validation specifically tailored to their biology. Without population-specific evidence, clinicians and families face uncertainty when symptoms overlap with other neurodevelopmental or age-related conditions.

A new USC-led study, published in Communications Medicine, addresses that gap. Researchers evaluated two blood-based biomarkers—Lumipulse G p-tau217/β-Amyloid 1-42 and PrecivityAD2—in participants with Down syndrome. Notably, Lumipulse G received FDA approval in 2025 to support Alzheimer’s diagnosis in the general population, but it had not been studied in Down syndrome until now.

The study enrolled 39 participants with Down syndrome. Each participant provided blood for both assays and underwent amyloid PET imaging, considered a reference standard for detecting brain amyloid pathology. The investigators reported that both blood tests reliably identified abnormal amyloid burden in the brain.

Using advanced statistical methods, the team derived preliminary diagnostic thresholds for Down syndrome. These cutoffs separated individuals with versus without Alzheimer’s pathology with accuracy comparable to what is observed in broader populations. In other words, the biomarker signal behaves in a way that can be translated into clinically actionable decision-making.

Beyond detection, the work suggests a workflow similar to general-population strategies: a positive blood result could be used to guide confirmation and downstream evaluation, while the blood test’s low false-negative rate supports its utility as an earlier screening layer.

Such screening has practical implications for families. Ruling out Alzheimer’s pathology may redirect clinicians toward other plausible drivers of cognitive or behavioral decline, including treatable medical conditions. It also strengthens trial recruitment by enabling biomarker-based eligibility selection.

The team plans further validation in a larger Down syndrome cohort. In parallel, the results are already poised to accelerate research, including an upcoming clinical trial of donanemab in people with Down syndrome, using elevated amyloid measured from blood to select participants.