Scientists have developed a new blood test that could make diagnosing Alzheimer’s disease faster, easier, and far less invasive—potentially opening the door for more patients to access emerging treatments.
Researchers from CSIRO, Australia’s national science agency, discovered that by combining two blood tests, doctors can detect Alzheimer’s disease with accuracy comparable to current “gold standard” methods such as brain scans and spinal fluid analysis.
The findings were published in Alzheimer’s & Dementia.
Until now, diagnosing Alzheimer’s has relied heavily on expensive PET scans or lumbar punctures, procedures that are either difficult to access or uncomfortable for patients.
These tests are needed to confirm the presence of amyloid plaques—sticky protein clumps in the brain that are a hallmark of the disease.
New Alzheimer’s drugs, including Donanemab, recently approved by the Therapeutic Goods Administration (TGA) for early-stage patients, require this confirmation before treatment can begin.
The new approach combines two blood-based measurements: one test detects a protein called phosphorylated tau 217 (pTau217), and the other measures the ratio of two amyloid proteins, Aβ42 and Aβ40.
When used together, these tests were able to identify Alzheimer’s pathology with more than 93% accuracy—matching the precision of traditional diagnostic methods.
Dr. James Doecke, a lead scientist from CSIRO’s Australian e-Health Research Center, said this represents a major step forward in Alzheimer’s care.
“With new treatments for Alzheimer’s now available, we urgently need accurate, scalable, and less invasive tests to find out who can benefit,” he explained. “Our findings show this blood test combination performs at the level needed to confirm Alzheimer’s disease in patients.”
The study analyzed blood samples from nearly 400 participants, collected as part of the Australian Imaging, Biomarker and Lifestyle (AIBL) Study of Aging.
These included both healthy volunteers and people showing signs of cognitive decline or Alzheimer’s disease. Researchers also examined participants who would be eligible for new therapies like Donanemab.
The results were striking. In the group eligible for treatment, the combined blood test achieved 99% sensitivity—correctly identifying nearly every patient who had Alzheimer’s-related brain changes. The test also reduced uncertain results by almost half, giving clinicians more confidence in diagnosis and treatment planning.
Professor Colin Masters from The Florey Institute, a co-author of the study, said the breakthrough could change how Alzheimer’s is diagnosed around the world. “This is an important step toward using blood tests not just in research, but in everyday medical practice,” he said.
If adopted widely, this blood test could dramatically reduce the need for costly scans and invasive procedures, helping more patients get an early and accurate diagnosis.
That, in turn, could ensure faster access to life-changing therapies and give families more time to plan for the future.
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