On 16 May 2025, the U.S. Food and Drug Administration (FDA) authorised the first-ever blood test to aid in the diagnosis of Alzheimer’s disease – a pivotal moment in the evolution of dementia diagnostics.
The test, Fujirebio’s Lumipulse G β-Amyloid Ratio (1-42/1-40) and p-Tau217 assay, is now cleared for use in adults aged 55 and older who show signs of cognitive impairment. While not a stand-alone diagnostic, it provides clinicians with a much-needed, less invasive tool to help determine whether a patient’s symptoms may be due to Alzheimer’s pathology – specifically the presence of amyloid plaques in the brain.
This regulatory milestone opens the door to earlier detection, more equitable access to testing, and improved clinical decision-making. It also raises an important question for the UK: how soon can we follow suit?
What the Test Does:
- The Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio measures two key proteins found in blood plasma:
- pTau217, a phosphorylated form of tau protein associated with the formation of neurofibrillary tangles
- β-amyloid 1-42m, which is involved in the development of amyloid plaques
The test calculates the ratio of these two proteins in plasma – a component of blood. Elevated pTau217 and decreased β-amyloid 1-42 are hallmark indicators of Alzheimer’s pathology. Previously, detecting these biomarkers required either PET imaging (expensive and not widely accessible) or lumbar punctures (invasive and often uncomfortable for patients). The new blood-based test offers a scalable, less invasive alternative with strong diagnostic performance.
According to multi-centre validation studies, the test demonstrated a:
Fewer than 20% of patients fell into the indeterminate zone, meaning most results were clearly positive or negative. For patients with indeterminate results, clinicians are advised to use follow-up PET or cerebrospinal fluid (CSF) testing.
Why This Matters:
The availability of a reliable blood test for Alzheimer’s has broad implications for patients, families, and health systems. A faster, simpler diagnostic process enables:
- Earlier therapeutic intervention, particularly as disease-modifying drugs become available
- Improved care planning and support services for patients and carers
- Better differentiation between Alzheimer’s and other causes of dementia, reducing misdiagnosis
- Stronger patient selection for clinical trials and treatment with anti-amyloid therapies
This test represents a critical tool in shifting the Alzheimer’s diagnostic journey from reactive and late-stage to proactive and early-stage – a longstanding goal of dementia strategies worldwide.
Regulatory Significance:
Until now, most Alzheimer’s biomarker tests operated under limited regulatory oversight or research use-only conditions. This FDA clearance, the first for a blood-based Alzheimer’s assay, marks a significant shift.
The agency found that Fujirebio’s blood test is “substantially equivalent” to the company’s previously cleared cerebrospinal fluid (CSF) test. The approval was granted following a 510(k) notification, a type of premarket submission made to the FDA to demonstrate that a new medical device is substantially equivalent to a legally marketed predicate device. This pathway allows innovative tests to be introduced efficiently while maintaining safety and effectiveness standards.
The clearance also comes at a critical time when multiple new Alzheimer’s treatments are reaching the market, increasing the need for accurate, scalable diagnostics to confirm amyloid pathology and guide treatment decisions.
Implications for the UK:
While the test is not yet approved by the UK Medicines and Healthcare products Regulatory Agency (MHRA), its clearance in the U.S. signals a wave of innovation that could soon reach the UK.
Here are four forward-looking implications for UK healthcare:
Global Momentum
Fujirebio’s test is the first, but it will not be the last. Other companies, including C2N Diagnostics, Quest Diagnostics, and Eli Lilly, have developed blood-based assays and submitted them for regulatory approval. The Alzheimer’s Association has also announced that it will release new clinical guidelines on the appropriate use of blood biomarkers at its international conference this summer.
This momentum reflects a global transformation in how we detect and manage neurodegenerative diseases. The hope is that blood-based diagnostics will become routine, just as cholesterol tests are in cardiovascular care.
Looking Ahead:
For clinicians, patients, and policymakers in the UK, this is a moment of opportunity. The FDA’s decision underscores the growing scientific and clinical confidence in blood-based biomarkers as valid tools for supporting Alzheimer’s diagnosis.
The next step will be to evaluate these technologies through UK regulatory and policy frameworks, consider their integration into NHS services, and ensure that infrastructure is in place to support widespread use.
Read the full FDA announcement here.
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