Research indicates that two widely used diagnostic tests can accurately detect amyloid pathology in a high-risk population often excluded from clinical trials.
Scientists at the University of Southern California (USC) have found that two blood tests used to detect early markers of Alzheimer’s disease are effective for people with Down syndrome, according to a study published in Communications Medicine.
People with Down syndrome face a lifetime risk of Alzheimer’s disease exceeding 90%, yet they have historically been excluded from diagnostic research. The study evaluated Lumipulse G p-tau217/β-Amyloid 1-42, which received Food and Drug Administration (FDA) approval in 2025, and PrecivityAD2, a test currently used in research settings. Both tests were found to accurately detect Alzheimer’s pathology in this population, according to the study.
“These blood tests are revolutionizing the field,” says Michael Rafii, MD, PhD, professor of clinical neurology at the Keck School of Medicine of USC and medical director of the USC Epstein Family Alzheimer’s Therapeutic Research Institute, in a release. “Our work is one step toward making them available to people with Down syndrome. We’re encouraging clinicians to use the tests to help families understand the basis for symptoms they might be observing.”
The Link Between Down Syndrome and Amyloid
Down syndrome is caused by duplicated genetic material that leads to higher levels of amyloid plaques in the brain. By age 40, nearly all individuals with Down syndrome have these plaques, and the disease is the leading cause of death for this population over the age of 35, the researchers note.
“Being inclusive of this group is not only a scientific imperative, but also an ethical one,” says Rafii in the release. “This population taught us so much about the biology of Alzheimer’s. It’s sad, and wrong, to see them excluded from clinical trials.”
Study Methodology and Results
The research, conducted in collaboration with the University of Madison–Wisconsin and C2N Diagnostics, involved 39 participants with Down syndrome. Investigators compared blood tests measuring amyloid buildup and the p-tau217 protein against positron-emission tomography (PET) scans, which are considered the gold standard for diagnosis.
The investigators found both blood tests accurately detected the presence of abnormal levels of amyloid plaques in the brain, according to the study. By applying statistical techniques, the researchers established preliminary diagnostic thresholds specifically for patients with Down syndrome, achieving accuracy levels similar to those seen in the general population.
Improving Diagnostic Accessibility
Currently, Alzheimer’s diagnostics for this population are largely limited to amyloid PET scans, which involve radiation exposure and are typically available only at specialized centers, or lumbar punctures to evaluate spinal fluid.
“The blood test is much more accessible as a screening test,” says Zinayida Schlachetzki, MD, PhD, clinical research program administrator at the USC Epstein Family Alzheimer’s Therapeutic Research Institute, in a release. “It is easier to perform, less expensive, and readily scalable, and it places substantially less burden on patients.”
The study authors suggest that positive blood-based results could be confirmed with PET imaging, an approach already used for the general population. These findings will have an immediate impact on research; starting next month, investigators will use blood testing to select eligible participants for a clinical trial of the FDA-approved Alzheimer’s treatment donanemab in people with Down syndrome.
