FDA Clears First Blood Test for Early Detection of Alzheimer-Linked Amyloid Plaques

The FDA approved marketing for the first in vitro diagnostic device that tests blood to aid in diagnosing Alzheimer disease. | Image Credit: Pixelcrafts - stock.adobe.com

The FDA has cleared the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio, the first blood test to aid in diagnosing Alzheimer disease by detecting amyloid plaques, offering a less invasive and more accessible alternative.1

The Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio (Fujirebio Diagnostics, Inc) is the first in vitro diagnostic device that tests blood to aid in diagnosing Alzheimer disease in adult patients aged 55 years and older who are exhibiting signs and symptoms of the disease. Alzheimer disease is a progressive brain disorder that slowly destroys memory and thinking skills, often preventing the ability to carry out tasks over time. Detecting the presence of plaque and other evaluations shows that amyloid plaques found in a patient’s brain can clearly indicate Alzheimer disease.

Amyloid positron emission tomography (PET) brain scans detect and visualize amyloid plaques, typically years before clinical symptoms onset, to aid in diagnosing Alzheimer disease. However, PET scans consume time and expose patients to radiation. The national average for a PET scan is about $4637 for patients without insurance while patients with Medicare Part B still pay 20% of the approved amount if they meet the deductible.2

“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,” Martin A. Makary, MD, MPH, FDA commissioner, said in a statement.1

The Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio measures 2 proteins, pTau217 and β-amyloid 1-42, found in human plasma, and calculates the numerical ratio of the levels of the 2 proteins. This ratio reduces the need for a PET scan because it is correlated to the presence or absence of amyloid plaques in the patient’s brain. Unlike previous FDA-authorized tests, this new Lumipulse test only requires a simple blood draw, making it less invasive and much easier for patients to access.

The FDA evaluated data using the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio in a multicenter clinical study of 499 individual plasma samples from adults who were cognitively impaired. The Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio tested the samples, and researchers compared the results with amyloid PET scan or cerebrospinal fluid (CSF) sample test results.

Individuals with Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio–positive results (91.7%) had the presence of amyloid plaques by PET scan or CSF test result, and individuals with negative results (97.3 %) had a negative amyloid PET scan or CSF test result. Less than 20% of the 499 patients tested received an indeterminate Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio result.

These findings demonstrate that the new blood test can reliably predict the presence or absence of amyloid pathology associated with Alzheimer disease at the time of the test among patients with cognitive impairments. Potential risks with the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio are the possibility of false positive and false negative test results. False positive results could lead to an inappropriate diagnosis or unnecessary treatment, which could result in psychological distress, delay in receiving the correct diagnosis, cost expenses, and the risk for adverse effects from treatment.

The FDA found that the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio is substantially equivalent to the Lumipulse G β-amyloid Ratio (1-42/1-40), which is the previously authorized test that uses CSF samples. The FDA granted Breakthrough Device designation to the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio, a process designed to expedite the development and review of devices that provide for more effective treatment or diagnosis of life-threatening or irreversibly debilitating diseases or conditions.

The FDA's approval of donanemab-azbt for the treatment of adults with early symptomatic Alzheimer disease occurred almost a year before this authorized device.3 Kisunla, developed by Eli Lilly and Company, is the first and only amyloid plaque-targeting therapy approved for early Alzheimer disease. The FDA's controversial accelerated approval of the drug in January 2023 for the treatment of Alzheimer disease preceded Biogen's discontinuation of aducanumab.

“Today’s clearance is an important step for Alzheimer disease diagnosis, making it easier and potentially more accessible for US patients earlier in the disease,” Michelle Tarver, MD, PhD, Center for Devices and Radiological Health Director, said in a statement.1

References

1. FDA clears first blood test used in diagnosing Alzheimer’s disease. News release. FDA; May 16, 2025. Accessed May 19, 2025. https://www.fda.gov/news-events/press-announcements/fda-clears-first-blood-test-used-diagnosing-alzheimers-disease

2. Madison B. How much is a PET scan? Costs with or without insurance. GoodRx. November 1, 2023. Accessed May 19, 2025. https://www.goodrx.com/health-topic/diagnostics/pet-scan-cost

3. Jeremias S. FDA approves donanemab for early Alzheimer disease. The American Journal of Managed Care®. July 2, 2024. Accessed May 19, 2025. https://www.ajmc.com/view/fda-approves-donanemab-for-early-alzheimer-disease