Memorandum
- From
- Caroline Mercer via TIME.com
- Date
- Filed
- Society·6 min to read
- Re
New Alzheimer's Blood Tests Expand Access, but Experts Warn Against Screening Healthy Adults
ReNew Alzheimer's Blood Tests Expand Access, but Experts Warn Against Screening Healthy Adults
Four FDA-cleared blood tests can now detect early signs of Alzheimer's disease, offering a less invasive and more accessible alternative to brain imaging and spinal taps. But experts stress the tests are only for people with cognitive symptoms, not for screening healthy adults.
Four blood tests cleared by the U.S. Food and Drug Administration can now detect the earliest biological signs of Alzheimer's disease, marking a significant shift in how the condition is diagnosed. The tests offer a less invasive, less expensive alternative to brain imaging and spinal fluid analysis, and two of them cleared in August are designed to be more widely available to doctors and usable in younger patients for the first time.
The advance is being welcomed by researchers who see it as a step toward personalizing Alzheimer's care in the way cancer treatment is tailored to individual patients. «This is a very exciting time for the field,» said Dr. Eric Reiman, CEO emeritus and lead researcher at the Banner Alzheimer's Institute in Phoenix. «We're going to start personalizing Alzheimer's care similar to cancer, where we can inform diagnosis, prognosis, and staging to further inform disease severity.»
For decades, the only way to confirm Alzheimer's was through autopsy after death, when pathologists could identify amyloid plaques in the brain. Doctors now rely on a combination of patient and caregiver reports, cognitive tests, brain imaging, and spinal fluid tests. Some of those measures can be subjective, invasive, expensive, or difficult to assess. The blood tests are intended to address those gaps.
The first Alzheimer's blood test, made by Fujirebio, was cleared by the FDA in May 2025. It measures the ratio of two key proteins — a form of beta amyloid and a form of tau — to indicate whether amyloid plaques are accumulating in the brain. However, it requires specialized equipment and is not widely available in commercial labs. A second test, made by Roche and cleared in October 2025, detects a version of tau that correlates with amyloid buildup and was the first that primary care physicians could prescribe to rule out the disease.
The two newest tests, cleared in August, aim to make diagnosis easier and more accurate. PrecivityAD2, from the diagnostics company C2N, uses mass spectrometry to detect amyloid and tau with greater sophistication than traditional assays. It provides a probability score reflecting how likely a person is to have amyloid plaques. Major laboratories, as well as specific clinic and health system labs, can perform it, making it more widely available for doctors to prescribe. Because it was studied in younger populations with a higher family risk, it is the first test cleared for people as young as 40 who show signs of cognitive problems. Other blood tests are generally for people in their mid-50s or older.
«Because of the ability to go after individuals who represent the earliest stages of the disease process, we now have the opportunity to provide early diagnosis and then think about what should come next in managing that patient,» said Dr. Joel Braunstein, cofounder and CEO of C2N.
The other newly cleared test, Roche's Elecsys ptau217 plasma test, looks specifically for a changed version of tau called ptau217 that appears when amyloid starts to accumulate. For people with memory issues or other cognitive complaints, it can help determine whether the cause is likely Alzheimer's or something else. «It's the most useful test and has the highest sensitivity and specificity,» said Dr. Thomas Wisniewski, professor of neurology, pathology and psychiatry and director of the Alzheimer's Disease Research Center at NYU Langone Health. «We've been using these blood tests on the research side for a decade or so, so we have long experience knowing their utility.»
Despite the enthusiasm, experts are clear that the tests are not meant for everyone. All four are designed for people who are already showing signs or symptoms of memory loss or cognitive decline. They are not screening tools for healthy people with no symptoms to identify those at higher risk of Alzheimer's.
«I worry about them being used inappropriately, especially in patients without symptoms,» said Dr. Lawren VandeVrede, assistant professor of neurology at the University of California San Francisco. «One of the clear bright lines we have is that these tests are intended to identify the cause of cognitive symptoms in the context of an appropriate workup in which we look at medications, mood problems, and think of potential contributors to cognitive changes.»
VandeVrede noted that standard diagnostic workups without blood tests already achieve about 85% accuracy for Alzheimer's disease. Adding blood tests could improve that figure. But Wisniewski cautioned that the tests do not provide definitive answers. «These blood tests don't provide definitive answers; they provide information about risk,» he said. «So they are really for evaluating people with some sort of cognitive symptoms.»
5
