FDA Clears New Blood Tests for Alzheimer's, Expanding Diagnostic Options

The U.S. Food and Drug Administration (FDA) has cleared four blood tests for detecting the earliest signs of Alzheimer's disease, marking a significant advancement in diagnosing the neurodegenerative condition. These tests, which analyze key proteins associated with Alzheimer's, aim to provide earlier and more accessible diagnostic information.

Previously, definitive Alzheimer's diagnosis relied on post-mortem examination of the brain for amyloid plaques. Current diagnostic methods involve patient and caregiver reports on cognitive changes, cognitive tests, brain imaging, and spinal fluid analysis, but these can be invasive, expensive, or difficult to interpret.

Advances in Blood Testing

The first blood test cleared by the FDA, developed by Fujirebio, received clearance in May 2025. It measures the ratio of two crucial Alzheimer's proteins—beta-amyloid and tau—to indicate the presence of amyloid plaques in the brain. However, its reliance on specialized equipment limits its widespread availability.

In October 2025, a second test from Roche was cleared. This test detects a specific form of tau protein that correlates with amyloid plaque buildup and is designed for use by primary care physicians to help rule out Alzheimer's disease.

The two most recent tests, cleared in August, are intended to enhance the ease and accuracy of Alzheimer's diagnosis. PrecivityAD2, from diagnostics company C2N, utilizes mass spectrometry for more precise detection of amyloid and tau proteins. It provides a probability score for the presence of amyloid plaques and is available through major laboratories, making it more accessible to physicians. This test is also cleared for individuals as young as 40 who exhibit signs of cognitive problems, a younger demographic than the other blood tests, which are typically for individuals in their mid-50s and older.

The other newly cleared test, Roche's Elecsys ptau217 plasma test, specifically identifies ptau217, a modified tau protein that emerges as amyloid accumulates. This test assists patients with memory or cognitive complaints and their doctors in determining if Alzheimer's is the likely cause.

Who Should Consider These Tests?

Experts emphasize that these blood tests are intended for individuals experiencing symptoms of cognitive decline or memory issues. They are not designed for general screening of asymptomatic individuals to identify those at higher risk. The primary utility lies in investigating the cause of noticeable cognitive changes.

Dr. Lawren VandeVrede, an assistant professor of neurology at the University of California San Francisco, voiced concerns about the potential misuse of these tests in patients without symptoms. She stressed the importance of a comprehensive diagnostic workup that considers other potential contributors to cognitive changes, such as medications, mood disorders, and sleep issues. Historically, such evaluations have achieved about 85% diagnostic accuracy for Alzheimer's disease without blood tests, a figure that could be improved with the addition of these new biomarkers.

These blood tests provide information about risk rather than definitive answers, making them most valuable when evaluating individuals with existing cognitive symptoms, according to Dr. Thomas Wisniewski, professor of neurology at NYU Langone Health.

Future Applications and Limitations

Currently, the tests have not been extensively studied in individuals without cognitive problems, leading to uncertainty about their reliability, including potential rates of false positives or negatives, in this population. Research suggests that looking for Alzheimer's proteins in lower-risk individuals may lead to more inaccurate readings.

However, this landscape could evolve as two major studies investigate whether Alzheimer's drugs like lecanemab and donanemab can prevent or slow disease progression in individuals who show early biomarkers but no cognitive symptoms. If these trials prove successful, the blood tests could become crucial for identifying people in the very earliest stages of the disease, potentially enabling earlier intervention.

Published research indicates that a significant portion of cognitively intact older adults may exhibit positive Alzheimer's biomarkers. This suggests that blood tests could play a role in assessing brain health and Alzheimer's risk before symptoms manifest, opening possibilities for early treatment if supported by clinical trials.

Furthermore, these blood tests may be valuable in monitoring the effectiveness of Alzheimer's treatments by tracking reductions in brain plaques. A recent study in Alzheimer’s & Dementia found that patients taking lecanemab showed a decrease in ptau217 levels, which correlated with slower cognitive decline.

Differences and Accessibility

While all approved blood tests target hallmark Alzheimer's proteins, they differ in sensitivity and specificity, with ptau217 levels generally considered the most reliable indicator to date. PrecivityAD2's clearance for younger populations may make it particularly useful for individuals with a family history of the disease who are beginning to experience cognitive symptoms.

These blood tests are democratizing Alzheimer's diagnosis by empowering primary care physicians. Recent studies indicate that primary care doctors can effectively interpret and manage Alzheimer's diagnoses using these tests, aiding in the triage of patients who may require referral to specialists for further evaluation, such as PET scans or spinal fluid tests.

The Alzheimer's Association has developed guidelines to help primary care doctors interpret the tests. These guidelines advise confirming cognitive symptoms and ruling out other potential causes before ordering an Alzheimer's blood test. The association anticipates increased demand for these tests and emphasizes the importance of proper patient selection.