A newly developed blood test for Alzheimer’s disease can not only help diagnose the condition but also determine how far it has progressed, according to researchers from Washington University School of Medicine in St. Louis and Lund University in Sweden.
This breakthrough could help doctors choose the most effective treatments for each patient.
Several blood tests for Alzheimer’s are already available, including two based on WashU technology, but these only confirm the presence of the disease—they don’t indicate the stage of cognitive decline. Since current treatments work best in the early stages, knowing the disease stage is essential for tailoring care.
The new test measures levels of a protein fragment called MTBR-tau243 in the blood. This fragment reflects the amount of toxic tau tangles in the brain, a hallmark of Alzheimer’s, and closely correlates with symptom severity.
In the study, researchers showed that MTBR-tau243 levels could clearly distinguish between early- and late-stage Alzheimer’s, as well as separate Alzheimer’s cases from other forms of dementia.
Alzheimer’s disease develops in two major steps: first, the build-up of amyloid plaques in the brain; then, years later, the formation of tau tangles.
Symptoms usually appear around the time tau tangles begin to spread, worsening as they accumulate. The gold standard for measuring amyloid and tau is PET brain scanning, which is accurate but costly and inaccessible for many patients.
Blood testing offers a simpler alternative. In this study, MTBR-tau243 blood levels matched tau PET scan results with 92% accuracy.
The test was piloted in two groups—108 participants from WashU’s Alzheimer Disease Research Center and 55 from Sweden’s BioFINDER-2 study—then validated in a larger group of 739 people from BioFINDER-2. Participants represented nearly the entire Alzheimer’s spectrum, from presymptomatic individuals to those with full dementia.
Importantly, MTBR-tau243 levels stayed normal in healthy people and those in the presymptomatic stage (with amyloid plaques but no symptoms).
Among people with cognitive symptoms from Alzheimer’s, levels were elevated in mild cognitive impairment and up to 200 times higher in those with dementia. The test also ruled out Alzheimer’s in patients with symptoms caused by other conditions.
The underlying technology has been licensed to C2N Diagnostics, the same company that created the amyloid blood tests already in use. Researchers say MTBR-tau243 could be combined with another biomarker, p-tau217, to boost diagnostic accuracy. Positive results for both strongly indicate that Alzheimer’s is the cause of cognitive symptoms.
With more Alzheimer’s treatments becoming available—including drugs targeting amyloid and others in development aimed at tau—such staging tests could support a personalized medicine approach. For example, anti-amyloid therapies may be best in early stages, while anti-tau treatments could work better in later stages.
“We’re about to enter the era of personalized medicine for Alzheimer’s disease,” said co-author Kanta Horie, PhD. “Once we have a clinically available blood test for staging, doctors can match treatments to the patient’s disease stage, offering the best possible outcomes.”
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The study is published in Nature Medicine.
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