Alzheimer’s disease is a complex brain disorder that affects memory, thinking, and behavior, leading to disability and loss of independence. Currently, nearly 10% of Americans 65 or older, an estimated 7.2 million, are living with the Alzheimer’s disease (AD) which underscores the importance of diagnosis and treatment of AD.
On May 16, 2025, the US FDA approved a first in-vitro blood test for Alzheimer’s disease (AD) performed with Lumipulse G, a diagnostic device by Fujirebio Inc., a US based subsidiary of H. U. Group Holdings Inc., a Japanese company (market cap ~ 1.25B USD).
The device measures the ratio of AD biomarker proteins pTau217/ß-Amyloid 1-42 in plasma to determine the presence of amyloid plaques in the brain, a key indicator of Alzheimer’s disease.
AD pathology:
Tau is a vital protein in nerve cells essential for maintaining the structure and function of nerve cells. pTau 217 is tau protein phosphorylated at the 217th amino acid residue. This chemical change leads to the formation of neurofibrillary tangles of tau protein and has been used as a biomarker for detecting tau pathology in AD. β-Amyloid 1-42 is an Amyloid-beta peptide of 1-42 form and is a major component of amyloid plaques, another hallmark of AD. There is evidence that pTau217 could also be responsible in part in the formation of β-Amyloid plaques.
Clinical trial:
Clinical study in the development of this test involved 499 adults, aged 52 to 93 years, with confirmed amyloid pathology based on amyloid PET scan or cerebrospinal fluid (CF) testing, approved and stand-alone methods for confirming the presence of AD. To minimize false positives and negatives, study included two cut points, upper and lower protein ratio limits, to assign positive and negative AD pathology. Individuals with results between the two cut points were assigned “indeterminate” AD classification. Dual cut points improved the sensitivity (ability to correctly identify patients with AD) and specificity (ability to correctly identify patients without AD).
Compared to standard tests, the plasma test results identified 92% patients as AD positive and 97% patients as AD negative, demonstrating high degree of correlation with amyloid PET imaging and cerebrospinal fluid (CF) testing.
Per Fujirebio, plasma ratio test is indicated for use in adults 50 years or older whereas per FDA communication, the threshold is 55 years. FDA communication notes hat this test is not intended for screening asymptomatic patients but for those with confirmed AD.
LabCorp, a laboratory services company for individuals and healthcare providers, has already launched its pTau217/β-Amyloid 1-42 ratio test since April 2, 2025.
Blood test Vs. PET-CSF tests:
Blood test is a less invasive and quicker alternative to amyloid PET imaging or cerebrospinal fluid (CSF) test: A PET scan typically takes about 1.5-2 hours which includes uptake time taken by tracer to brain and imaging time. PET scanning requires a patient to lie still in a scanner for 15-20 minutes. A lumbar puncture, or spinal tap, is invasive and typically takes 15 to 30 minutes which includes patient preparation time and sample collection. Patient undergoing CF testing needs to stay in certain posture for about 15-20 minutes and typically needs to lie on the back or side for an hour to a few hours after the sample is taken. Blood test cost is expected to be lower than that of PET imaging or CSF test. Based on this analysis, blood test is relatively simple, convenient, requires less time and economical.
FDA notes in the approval press release that “ Plasma Ratio is not intended as a screening or stand-alone diagnostic test and other clinical evaluations or additional tests should be used for determining treatment options”. Indeed, potential for using this test for screening for AD, intentionally or otherwise, exists. Regarding the stand-alone aspect, around 20% of the clinical trial participants were the “indeterminate” classification, and would need PET scan or a CSF test to confirm the presence or absence of AD. It would be interesting to know the results of the standard tests for this population. If improvements to this test could be made in future to reduce the patients in the “indeterminate” classification, it would open the possibility to qualify this test as a stand-alone test.
AD PET tracers market:
Current PET tracers for AD visualize both amyloid plaques and tau tangles, providing information for diagnosis, staging, and monitoring disease progression. Examples include Vizamyl (GE Healthcare), Neuraceq (Lantheus Medical Imaging), Amyvid (Eli Lilly) and Tauvid (Eli Lilly). Sales figures for these PET tracers are not available as they are typically not separately disclosed in financial reports. However, based on one estimate prior to the approval of plasma ratio test, PET diagnostic market is projected to reach 1.5B USD by 2030.
