In many cases, it's not until memory problems start creeping up that most people learn they have Alzheimer's disease. By then, the disease may already be progressing, leaving limited options for managing the condition.
Now, a new diagnostic test reveals whether you're at higher risk of getting Alzheimer's disease, potentially years before the disease takes hold. In May 2025, the FDA approved a test called, "the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio." The test detects amyloid plaques in the blood, which are a hallmark of Alzheimer's disease. Although other available tests can detect blood-based biomarkers linked to Alzheimer's, this is the first approved by the FDA.
But the newly approved test has raised a number of questions: Can it definitively tell if you have Alzheimer's disease? If your test is positive, what can you do? Even more importantly, who should take the test?
To answer these questions, WebMD met with neurologists Ayesha Sherzai, MD, and Dean Sherzai, MD, PhD, the co-directors of the Alzheimer's Prevention Program at Loma Linda University in California. (The Sherzais also host Your Brain On, a podcast about brain health.) Below, the Sherzais explain how the test works and what it does – and doesn't – mean.
WebMD: Why is this new test getting so much attention? What's different about it?
Ayesha Sherzai: First, a little bit of a background about Alzheimer's disease. It is a neurodegenerative disease where there is degeneration of brain cells and their connections. It's not something that happens all of a sudden. It takes years, up to maybe 20 to 30 years, for the disease to
develop or to get to a point where people experience memory problems and the typical symptoms of dementia. So typically when a person goes to a neurologist, they get memory testing, neuroimaging, maybe some blood tests to look at risk factors that might increase the risk for Alzheimer's disease. But we really haven't had any diagnostic test to tell us specifically whether we are at a higher risk for developing Alzheimer's disease directly until now.
WebMD: What does the test show and how accurate is it?
Ayesha Sherzai: These FDA-approved blood tests essentially show a combination of different proteins that deposit in the brain and are responsible for the damage in the brain. And when you look at the different ratios of these proteins in the blood, you can tell with some degree of certainty that a person is at a higher risk of experiencing the symptoms of Alzheimer's disease. The test's accuracy is above 90%.
If somebody has a positive result, it means that they have probable Alzheimer's disease. But if they have a negative test, it doesn't mean that they don't have it. If it's negative, it most likely rules it out, but we still rely on our clinical experience, on neuropsychological testing, and on imaging to rule out definitive Alzheimer's disease cases.
WebMD: Is the approved test one test or a series of blood tests?
Ayesha Sherzai: While we often refer to it as "a blood test," it's really a panel of tests run on one blood draw.
WebMD: Are there any misconceptions out there about the test?
Dean Sherzai: The test [result] doesn't mean that you're going to succumb to Alzheimer's. It's degree of risk. It indicates a higher likelihood of amyloid pathology consistent with Alzheimer's disease, but it's not diagnostic on its own.
Also, the test is for Alzheimer's only. A negative result does not rule out other neurodegenerative conditions such as Lewy body disease, frontotemporal dementia, [or other conditions].
WebMD: Who should get this test?
Ayesha Sherzai: This test is not for everyone. It's for people who are 55 years and above and who are symptomatic. It's not for people who don't have any symptoms of memory disorder. You usually have to have some level of cognitive decline or memory problems. It is usually done at a doctor's clinic or a neurology clinic.
WebMD: How much does the test cost, and does insurance usually cover it?
Ayesha Sherzai: Insurance coverage is still limited and evolving. Most private insurers do not yet routinely cover these tests, though that may change as clinical guidelines evolve and [the Centers for Medicare & Medicaid Services] makes determinations. If a doctor orders the test as part of a diagnostic workup, some patients may get partial reimbursement, especially if they have symptoms like memory loss. Some companies offer financial assistance or sliding scale programs.
The cost of Alzheimer's blood tests can vary widely, depending on the lab and location, but most range from $500 to $1,200 if paid out of pocket.
WebMD: If your test is positive, what are your next steps?
Dean Sherzai: This blood test definitely demonstrates high risk. The next step would be to get the imaging as well as do the neuropsychological testing and cognitive testing, seeing where you are in the whole spectrum of the disease.
WebMD: What else should people know about this test?
Ayesha Sherzai: They [may want to] bring it up with their doctor because some doctors might not be updated that it's available. We want the public to be their own advocates. Sometimes, [specialists] in family medicine or internal medicine might not be aware of it. Have that conversation with them because they're usually the first ones to refer them for this testing or to send them to a neurologist if they have memory problems.
