A simple blood test may be able to identify the optimal time to begin treatment for Alzheimer’s disease, potentially helping patients receive newly available therapies when they are most effective, according to a new study.
Researchers from Yonsei University’s Gangnam Severance Hospital, Wonju Severance Christian Hospital and U.S.-based C2N Diagnostics found that blood levels of phosphorylated tau217 (p-tau217) can accurately predict both the stage of Alzheimer’s disease progression and the period during which treatment is likely to deliver the greatest benefit.
The study was led by Dr. Hanna Cho of the Department of Neurology at Gangnam Severance Hospital and Dr. Han Kyul Kim of Wonju Severance Christian Hospital in collaboration with researchers at C2N Diagnostics.
Alzheimer’s disease is a progressive neurodegenerative disorder characterized by the accumulation of amyloid proteins in the brain over decades, followed by the formation of tau protein tangles within neurons. As nerve cells become damaged and die, patients experience gradual declines in memory, language and cognitive function.
Recent advances in Alzheimer’s treatment have shifted the therapeutic landscape, with new drugs designed to remove amyloid plaques and slow disease progression. However, studies have shown that these therapies become less effective once the disease reaches advanced stages, making early identification of appropriate treatment candidates increasingly important.
Researchers have focused on identifying a so-called “therapeutic window” — a stage at which amyloid accumulation is already present but tau pathology remains in its early to intermediate phases. Patients treated during this period are believed to have the greatest potential to benefit from disease-modifying therapies.
To investigate whether a blood biomarker could identify that window, the research team analyzed 237 patients who underwent both positron emission tomography (PET) imaging and blood testing at the Memory Disorders Clinic of Gangnam Severance Hospital. The study population included cognitively normal individuals, patients with mild cognitive impairment (MCI) and those with Alzheimer’s dementia.
The analysis showed that blood p-tau217 levels accurately predicted both amyloid deposition and tau pathology in the brain. The biomarker achieved an area under the curve (AUC) of 0.96 for detecting early amyloid accumulation and an AUC of 0.92 for identifying moderate or greater tau pathology.
The findings suggest that a blood test could provide insights into underlying Alzheimer’s pathology with a level of precision approaching that of PET imaging, according to the researchers.
PET scans are currently among the most accurate methods for detecting amyloid and tau accumulation in the brain, but their widespread use is limited by cost, availability and patient access.
The team further developed a probability-based model to identify the stage at which treatment is likely to be most beneficial. According to the analysis, patients with blood p-tau217 levels between 1.895 and 5.077 pg/mL were most likely to have significant amyloid accumulation while remaining in the early-to-intermediate stages of tau pathology, making them strong candidates for disease-modifying therapy.
“Our findings provide evidence that a blood test can determine the stage of Alzheimer’s pathology with a level of accuracy comparable to PET imaging and help identify whether a patient has reached the optimal time to begin treatment,” Cho said.
She added that using blood testing as a first-line screening tool could improve efficiency and reduce healthcare costs by reserving PET imaging for patients who fall within the predicted therapeutic window.
The study was published in the peer-reviewed journal Alzheimer’s & Dementia, one of the leading international journals in Alzheimer’s disease research.
