Alzheimer’s: New Blood Test Predicts Onset Years in Advance

A new blood test is offering a potential glimpse into the future for individuals at risk of Alzheimer’s disease, predicting when symptoms are likely to begin years before cognitive decline becomes apparent. The test, described as a “clock model” by researchers, measures levels of specific proteins in the blood to estimate the trajectory of the disease.

The development, spearheaded by scientists at Washington University School of Medicine in St. Louis, represents a significant step forward in the early detection of Alzheimer’s. Currently, diagnosis often relies on identifying amyloid plaques in the brain – a hallmark of the disease – through costly and sometimes invasive methods like positron emission tomography (PET) scans. These scans can detect plaques years before symptoms emerge, but their expense and the radiation exposure associated with them limit their widespread use.

The new blood test focuses on two key proteins: pTau217 and β-amyloid 1-42. By measuring the ratio of these proteins in human plasma, a component of blood, the test provides a numerical assessment of Alzheimer’s risk. The “clock model” refers to the way the test predicts the timing of symptom onset, rather than simply indicating the presence or absence of the disease. Researchers are able to estimate, with increasing accuracy, how many years remain before an individual is likely to experience cognitive impairment.

The U.S. Food and Drug Administration May 16, 2025, cleared the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio for marketing as an in vitro diagnostic device to aid in the diagnosis of Alzheimer’s disease. This test is intended for use in adult patients aged 55 years and older who are exhibiting signs and symptoms of the disease. According to FDA Commissioner Martin A. Makary, M.D., M.P.H., “Alzheimer’s disease impacts too many people…Knowing that 10% of people aged 65 and older have Alzheimer’s, and that by 2050 that number is expected to double, I am hopeful that new medical products such as this one will help patients.”

Alzheimer’s disease is a progressive brain disorder that gradually destroys memory and thinking skills. While there is currently no cure, early detection is crucial for several reasons. It allows individuals and their families to plan for the future, participate in clinical trials, and potentially benefit from interventions aimed at slowing disease progression. The presence of amyloid plaques, while indicative of Alzheimer’s, can also occur in other conditions, highlighting the importance of considering the test results alongside other clinical evaluations.

The development of this blood test addresses a critical need for more accessible and affordable diagnostic tools. PET scans, while effective, are not readily available to everyone. The blood test offers a less invasive and more cost-effective alternative, potentially enabling wider screening and earlier intervention.

The FNIH Biomarkers Consortium study demonstrated the predictive power of the “clock model” blood test, showing its ability to forecast the onset of Alzheimer’s symptoms years in advance. This research builds upon previous work identifying pTau217 as a promising biomarker for Alzheimer’s disease. The test’s accuracy is continually being refined as researchers gather more data and refine the algorithms used to interpret the protein ratios.

Labcorp has recently launched its own Alzheimer’s blood test, and has also expanded its neurology offerings, sparking debate around the company’s valuation. This indicates growing commercial interest in the field of Alzheimer’s diagnostics.

While the blood test represents a significant advancement, it’s important to understand its limitations. It is not a definitive diagnosis on its own. A positive result should be interpreted in the context of a comprehensive clinical evaluation, including a review of medical history, neurological examination, and potentially other diagnostic tests. The test is most effective for individuals already exhibiting some signs or symptoms of cognitive decline.

The availability of this blood test marks a turning point in the fight against Alzheimer’s disease. By enabling earlier detection and risk assessment, it empowers individuals and healthcare providers to proactively address this devastating condition. Continued research and development will undoubtedly lead to even more accurate and effective diagnostic tools in the years to come, offering hope for a future where Alzheimer’s disease can be prevented or effectively managed.