FDA clears first blood test for Alzheimer's: How does it work?

Medical News Today

22-05-2025

The FDA has cleared the first blood test to diagnose Alzheimer's disease. Bowery Image Group Inc./Stocksy The earlier Alzheimer's disease can be diagnosed, the better the outcomes; however, it can be hard to diagnose the disease in its earliest stages.
The United States Food and Drug Administration recently cleared the first blood test to help diagnose Alzheimer's disease.
The new test measures the amount of proteins amyloid-beta and tau in the blood, and is less invasive than the currently used spinal tap to measure levels of these proteins in cerebrospinal fluid.
Like all diseases, the sooner Alzheimer's disease is diagnosed, the better the outcome. This is partially because medications available for the condition aim to treat symptoms and potentially slow the progression of the disease.
Despite all these tools, it can be hard to diagnose Alzheimer's disease, especially at its earliest stage .
According to the FDA's press release , the Lumipulse blood test works by measuring the amount of pTau 217 and beta-amyloid 1-42 in the plasma of the blood. The concentration ratio of the two proteins is used to determine the presence or absence of amyloid plaques in the brain, which is considered a hallmark of Alzheimer's disease.
'Imagine your brain is like an organized library, with information neatly stored on shelves (neurons),' Manisha Parulekar, MD, FACP, AGSF, CMD, director of the Division of Geriatrics at Hackensack University Medical Center and co-director of the Center for Memory Loss and Brain Health at Hackensack University Medical Center in New Jersey explained to Medical News Today. 'In Alzheimer's disease, two troublesome proteins, beta-amyloid and tau, disrupt this organization, making it hard to access the information.'
'Think of beta-amyloid as sticky notes that clump together between the bookshelves (outside the neurons),' Parulekar continued.
'These clumps, called plaques, interfere with communication between the neurons, like blocking pathways in the library. Tau is normally like a librarian, helping to keep the bookshelves (internal neuron structure) stable and organized. In Alzheimer's, tau becomes twisted and tangled. These tangles disrupt the transport of nutrients and other essential materials within the neurons, eventually leading to their death,' she said.
'In simple terms, this blood test helps identify the 'culprits' responsible for Alzheimer's damage, allowing for earlier diagnosis, better disease management, and faster development of effective treatments.'
— Manisha Parulekar, MD, FACP, AGSF, CMD
Up until now, the main laboratory test to check levels of amyloid-beta and tau proteins was by examining a sample of a person's cerebrospinal fluid (CSF). The sample is taken through a lumbar puncture — also known as a spinal tap — where a needle is inserted into a person's lower spine.
Gediminas Gliebus, MD, director of cognitive and behavioral neurology at Marcus Neuroscience Institute, a part of Baptist Health South Florida, told MNT having a test requiring a blood sample instead of a CSF sample significantly simplifies the testing process, eliminating the need for invasive and costly procedures like lumbar punctures, which can deter some patients from seeking evaluation.
'By relying on a simple blood sample, this test makes it more accessible to a broader population, facilitating earlier diagnosis and enabling timely interventions that could help manage the progression of the disease. This new test has the potential to change how we diagnose Alzheimer's disease by streamlining the process and reducing the need for more invasive procedures.'
— Gediminas Gliebus, MD
'Based on the scientific data provided by the company, only 20% of patients would require additional invasive and costly tests, such as lumbar punctures or PET scans, to confirm the diagnosis. This is a significant improvement, as it allows the majority of patients to receive a preliminary evaluation with minimal discomfort and expense, fostering early detection and intervention,' Gliebus explained.
As part of their approval announcement, the FDA stated risks associated with the Lumipulse blood test include both false positive and negative results.
For that reason, all of the experts we spoke with agree that while this new test is a promising diagnostic tool, it is not the only tool that should be used and more research is still needed.
'This test has potential for use in pre-screening participants in clinical trials for early stages of Alzheimer's disease, however, its application in primary care settings is not yet fully understood, and further research is needed before it is used as a screening tool for the general population,' Bhavana Patel, DO, assistant professor of neurology at the University of Florida explained to MNT . Things to keep in mind about the test
'As with many tests, false positives and false negatives can occur. Therefore, this test should be done in the setting of cognitive symptoms and with a specialist who can accurately interpret and counsel on the results.'
— Bhavana Patel, DO,
'My first response to this blood test is concern (that) primary care physicians are going to diagnose patients with Alzheimer's dementia from a blood test who have no memory loss or risk factors for dementia,' added Clifford Segil, DO a neurologist in private practice in Santa Monica, CA, and on staff at Providence St John's Health Center.
'And tests like this, which were not approved by the typical rigorous FDA pathway, but rather through an abbreviated process via the FDA's ' Breakthrough Pathway ,' which cause me concern countless people are going to be told they have dementia per a blood test when they do not have dementia,' he said.
'Neurologists in clinical practice have found similar tau and amyloid biomarkers to have a high percentage of false positives in clinical practice and do not rely only on a blood test to diagnose a family member or you with dementia,' Segil told MNT . 'Neurologists are unlikely to use these tests, which will be used by primary care physicians. If you do get a positive result from a blood tau or amyloid test, please be evaluated by a neurologist to determine if they have any clinical significance.'
With some questions still to be answered regarding the Lumipulse blood test, many experts expressed their hope that it will provide more assistance in the early diagnosis of Alzheimer's disease.
'This is an exciting time in the field, as we now have a noninvasive, easily accessible test that can help identify Alzheimer's disease in individuals experiencing memory changes,' Patel said. 'Having an easily accessible blood test will allow for an earlier diagnosis in those with cognitive changes and serve as an opportunity for participation in clinical trials and receive treatments that may impact disease progression.'
'I was genuinely excited to hear about the FDA's [clearing] of this blood test, as it represents a significant advancement in simplifying the evaluation of patients who present with symptoms that might suggest Alzheimer's disease,' Gliebus commented. 'This test offers a less invasive and more accessible way to evaluate the condition, potentially transforming how we approach early diagnosis and patient care.' Lower cost, less invasive
'The less invasive nature of a blood test will likely encourage more people experiencing mild cognitive impairment or early symptoms to seek testing. Earlier diagnosis is crucial for maximizing the effectiveness of current and future treatments. The simplicity and lower cost of blood tests compared to PET scans or spinal taps will make testing more accessible to wider populations, including those in underserved communities or without easy access to specialized medical centers. This could lead to earlier diagnosis for individuals who might otherwise go undiagnosed for years.'
— Manisha Parulekar, MD, FACP, AGSF, CMD
'We do have to follow appropriate steps in the diagnosis and make sure to use this as a diagnostic tool — this is not a screening test. It's a tool that holds promise — its true impact will depend on how it's integrated into clinical practice,' Parulekar added.