What to Know about a New Blood Test for Alzheimer’s

Alzheimer's disease is a heartbreaking and complicated condition, slowly taking away memory, thinking, and independence. While we still have a lot to learn, researchers at Columbia University are working to make early detection easier.

Zhonghua Liu, ScD, a senior investigator and assistant professor of biostatistics at Columbia's Mailman School of Public Health, uses advanced methods to understand the genetics behind Alzheimer's. His work helps identify proteins in the blood that may signal early signs of the disease, which could lead to earlier diagnosis or better treatment.

Last spring, the U.S. Food and Drug Administration (FDA) approved the first blood test to help diagnose Alzheimer’s. And recently, the Alzheimer’s Association released its first clinical practice guideline on the use of blood-based biomarker tests by specialists to assess levels of Alzheimer’s disease in patients with confirmed cognitive impairment. These guidelines recommend that blood tests with over 90% sensitivity and specificity can replace more invasive methods—like a positron emission tomography (PET) imaging test or spinal taps—to rule out Alzheimer’s but will require follow-up for positive results. The recommendations emphasize that blood tests should supplement—not replace—a full clinical evaluation and only apply to patients already under a specialist’s care.

Dr. Liu explains how the new FDA-approved test works and the ways it can benefit patients.

What is Alzheimer's disease—and is it genetic?

Alzheimer's is a brain disease that slowly affects memory, thinking, and the ability to do everyday tasks. It's the most common form of dementia in older adults.

While getting older is the biggest risk factor, genes also play a role. Having a parent or close relative with Alzheimer's doesn't mean you'll definitely get it—but it can increase your risk.

What are the early symptoms of Alzheimer’s?

Some symptoms often start small but can worsen over time. The symptoms include:

• Trouble remembering recent events or conversations
• Confusion about time or place
• Difficulty finding words or understanding others
• Struggling with everyday tasks
• Changes in mood or personality

What's the new blood test—and how does it work?

The first FDA-approved blood test to help doctors diagnose Alzheimer's disease is called the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio. FDA approval means the test has been carefully reviewed for accuracy and safety so that doctors can use it in regular medical practice.

This test looks for two key proteins in the blood—pTau217 and beta-amyloid 1-42—that are linked to Alzheimer's. When these proteins build up in the brain, they form plaques, a hallmark of the disease. The test measures the ratio of these proteins to help doctors tell whether a person may have these plaques.

Who is this test for?

The test is intended for adults 55 and older who are already experiencing memory issues or cognitive symptoms. It is not meant for healthy people or general screening.

What do the test results show?

The test doesn't give a clear "yes" or "no" answer as to whether a patient has Alzheimer’s, but it can show if someone may have early signs of amyloid plaques in the brain. Your doctor may use the results to decide whether further testing—like brain scans or memory evaluations—is needed.

Think of the blood test as one important piece of the puzzle.

How is this different from existing Alzheimer's tests?

Older tests to detect Alzheimer’s can be expensive or uncomfortable. They include spinal fluid tests (spinal taps), PET brain scans, and cognitive or memory assessments.

Because the new test only requires a simple blood draw, it's less invasive and more convenient than existing tests.

Is this the only blood test for Alzheimer’s?

Other blood tests are being evaluated in research or limited clinical settings. But this is the first one approved by the FDA. However, more tests may be approved and become available soon for clinical use.

If a blood test detects the signs of Alzheimer’s, is there early treatment that can help?

Right now, FDA-approved treatments such as donanemab (Kisunla) and lecanemab (Leqembi) are only approved for people who already have mild Alzheimer’s symptoms, such as mild cognitive impairment or mild dementia. These drugs were studied in patients who already had memory or thinking problems, not in people who are symptom-free.

If a blood test shows signs of Alzheimer’s before symptoms appear, called the “pre-clinical stage,” there is currently no approved treatment.

What's next in Alzheimer's research?

We are working to make blood tests even more accurate, accessible, and useful earlier in the disease process, when treatments and prevention may be most effective.

We are also exploring how genes, proteins, and protein shapes contribute to Alzheimer's. Using advanced tools like AlphaFold3 (an AI program), we can predict the 3D structure of proteins to uncover new targets for treatment.

What excites me is bringing together leading-edge genetics and data science tools to understand this disease better—and hopefully make a real difference for patients and families.

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Zhonghua Liu, ScD, is a senior investigator and assistant professor of biostatistics at Columbia's Mailman School of Public Health.