New blood tests that detect early changes associated with Alzheimer's disease are making diagnosis easier and more accessible, as they are less invasive than the brain scans or spinal taps typically used for a definitive diagnosis. Identifying the condition in its earlier stages means drugs that slow progression may have the chance to provide greater benefit, according to a July 27 announcement.
However, one group at elevated risk is rarely included in testing advances. Alzheimer's incidence is dramatically higher in people with Down syndrome. Yet Lumipulse G p-tau217/β-Amyloid 1-42, a blood test approved by the Food and Drug Administration in 2025 to aid in the diagnosis of Alzheimer's disease, is not available to them because it has not been studied in that population.
Scientists at the USC Epstein Family Alzheimer's Therapeutic Research Institute aim to change that. A new USC-led study published in Communications Medicine is the first to engage participants with Down syndrome to evaluate Lumipulse G p-tau217 and PrecivityAD2, another blood test already widely used for research. The researchers found both tests are effective in detecting Alzheimer's pathology among this population.
"These blood tests are revolutionizing the field," said 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. "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."
Down syndrome causes higher levels of amyloid plaques due to duplicated genetic material; by age 40 almost all people with Down syndrome have amyloid plaques present. Not all will develop Alzheimer's disease but lifetime risk exceeds 90%, and it remains a leading cause of death among those over age 35.
The study involved collaboration between scientists from USC, University of Wisconsin–Madison, and C2N Diagnostics—the maker of PrecivityAD2—and included 39 participants with Down syndrome. Blood from each participant was tested using both Lumipulse G p-tau217 and PrecivityAD2 assays; each also underwent positron-emission tomography (PET) scanning, considered the gold standard for Alzheimer’s diagnosis.
Researchers found both blood tests accurately detected abnormal levels of amyloid plaques within participants’ brains. Applying advanced statistical techniques allowed investigators to establish preliminary thresholds specific for people with Down syndrome—achieving nearly equivalent accuracy as seen within general populations.
Currently available diagnostics include amyloid PET scans or lumbar puncture procedures; these methods can be less accessible or involve additional risks compared with simple blood draws. "The blood test is much more accessible as a screening test," said Zinayida Schlachetzki, MD, PhD, clinical research program administrator at USC Epstein Family Alzheimer’s Therapeutic Research Institute. "It is easier to perform, less expensive and readily scalable, and it places substantially less burden on patients." In general populations, positive results from such tests are confirmed via PET imaging—a strategy which may also apply here given low rates of false negatives observed among study subjects.
"There's a huge value to families in ruling out Alzheimer’s disease," Rafii said. "Doctors can then search after some other cause for symptoms such as untreated depression or undiagnosed sleep apnea." Researchers plan further evaluation within larger cohorts while launching next month a clinical trial using donanemab—an FDA-approved treatment—in people with Down syndrome selected through these new testing protocols.
