On May 16, 2025, the FDA granted its first authorization to the Lumipulse G blood test, which uses the plasma ratio pTau217/Aβ1-42, for diagnosing amyloid plaques in symptomatic patients aged 55 and older. The test predicts the onset of Alzheimer’s symptoms with a median absolute error of 3.0 to 3.7 years. The test makes it possible to identify the pathology before cognitive disorders appear.
Given that 10% of people aged 65 and older suffer from Alzheimer’s, and this figure is expected to double by 2050, this first blood test approved by the FDA transforms accessibility to diagnosis of a disease that currently affects 55 million people worldwide.
92% Accuracy for Detecting Amyloid Plaques
In clinical validation, concordance rates with brain amyloid PET scans and cerebrospinal fluid biomarker detection results were 91.7% (positive) and 97.3% (negative). The plasma p-tau217 test detects Alzheimer’s pathology with receiver operating characteristic curve areas of 0.93 to 0.96.
The Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio measures two proteins, pTau217 and β-amyloid 1-42, found in human plasma, and calculates the numerical ratio of the levels of both proteins. The main advantage: simplicity and reliability compared to previous methods.
PET scans remain an expensive and time-consuming option that exposes patients to radiation. This new Lumipulse test requires only a simple blood draw, making it less invasive and much more easily accessible to patients.
A Detection Window of 3 to 4 Years Before Symptoms
By measuring a protein called p-tau217, the model predicts the onset of symptoms within approximately three to four years. A person with elevated p-tau217 at age 60 would develop symptoms approximately 20 years later. Meanwhile, a person whose p-tau217 becomes elevated at age 80 would develop symptoms after only 11 years.
Previous research has shown that plasma p-tau217 closely reflects the accumulation of amyloid and tau in the brain, as observed on PET scans. It is the earliest risk detection biomarker, more than 20 years in advance.
Data from more than 8,500 people in the United States and the Dominican Republic show that people with one or two copies of the Alzheimer’s risk gene APOE4 plus elevated p-tau217 levels develop cognitive symptoms within 3 to 4 years following the test.
The Economic Equation That Transforms Access to Care
The test can reduce the need for lumbar punctures or PET scans that cost over $10,000. The cost-neutral price would be $290 for a screening test and $1,150 for a confirmatory test in primary care settings in 2025.
CMS has finalized a reimbursement rate of $130 for newly FDA-approved blood tests that detect Alzheimer’s biomarkers. These blood tests cost 80 to 90% less than traditional diagnostics.
Compared to PET scans (when access is unlimited), the blood biomarker screening test could identify nearly all (98.2%) of PET+ patients at a lower average cost per PET+ diagnosis ($8,868 versus $10,345 per PET+ diagnosis). Diagnosis becomes accessible to a much broader population.
Alzheimer’s blood biomarkers are particularly useful where invasive and complex diagnostics are unavailable, notably in rural areas and under-resourced health systems.
Challenges of Clinical Integration and Equity
An American physician testifies: almost every time she prescribes this test, she must also help her patients fill out a financial assistance form. FDA approval is not enough to overcome economic barriers.
Black Americans are twice as likely, and Latino Americans one and a half times as likely, to develop dementia as white Americans. More available and more affordable means of diagnosing Alzheimer’s disease could help these groups of people.
Regions with low and medium SDI (sociodemographic index) may experience significant under-diagnosis due to limited access to healthcare and stigma, alongside higher competing risks of mortality from other causes. Technological innovation alone solves nothing without equitable access policies.
Currently, the p-tau217 blood test is not recommended for cognitively normal individuals. It should not be used as a standalone tool for diagnosing Alzheimer’s.
The Therapeutic Horizon That Justifies Early Detection
Over the past two years, two new drugs—Kisunla and Leqembi—have become available and reduce Alzheimer’s amyloid pathology and slow disease progression. This makes obtaining a reliable diagnosis more important than ever, as these new drug therapies are highly specific to Alzheimer’s pathology and can only be prescribed to patients with elevated amyloid levels in the brain.
Early diagnosis means early treatment, potentially slowing cognitive decline by 30 to 60% in eligible patients. Early detection thus shifts from prognosis to concrete intervention.
This hypothesis drives an ongoing trial called TRAILBLAZER-3, in which people with positive p-tau217 but no symptoms take the anti-amyloid drug donanemab to see if it delays the onset of cognitive impairment.
The p-tau217 test opens a 3 to 4 year window to intervene before the first symptoms appear, in a disease that could affect 152 million people by 2050. It remains to be seen whether access will follow science—the new anti-amyloid therapies only work with early and accurate diagnosis.