Detecting Alzheimer’s Through Blood Tests: What You Need to Know

The way doctors detect signs of Alzheimer’s disease is quickly changing. In August, the FDA cleared two new blood tests designed to help identify Alzheimer’s-related changes in the brain, bringing the total number of FDA-cleared blood tests from two to four. While a blood test cannot independently diagnose Alzheimer’s disease, these advances could offer physicians a simpler, less invasive way to determine whether Alzheimer’s-related amyloid plaques may be contributing to a patient’s memory or cognitive decline. Here are the details…

Already available blood tests:

• Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio – This blood test was the first cleared in 2025 and measures a combination of tau and amyloid biomarkers in the blood.
• Elecsys pTau181 – This blood test, also cleared in 2025, measures a specific form of tau and is primarily used to help rule out Alzheimer’s-related amyloid pathology… meaning a negative result can help physicians look toward other possible causes of cognitive decline.

NEW available blood tests:

• Elecsys pTau217 – This blood test measures a single blood biomarker but can help physicians both rule in and rule out the likelihood of amyloid pathology. This test can be used in primary-care as well as specialty-care settings.
• PrecivityAD2 – This blood test takes a different approach by measuring both amyloid- and tau-related biomarkers and combines that information into a score indicating the likelihood that amyloid plaques are present. This test differentiates from the other three because it is intended for adults showing cognitive impairment symptoms beginning at age 40, compared with age 55 for the other tests.

Why does this matter? Until recently, confirming Alzheimer’s-related changes often relied on more expensive or invasive testing, including PET brain scans or analysis of spinal fluid. Blood-based testing helps to make the diagnostic process more accessible and easier to incorporate into routine medical care, helping physicians determine who may need additional evaluation or have disease pathology present. Early detection is becoming increasingly important as the current available FDA approved Alzheimer’s disease treatments are designed for people in the earliest stages of the disease.

It is important to keep in mind that while these tests are a great step forward in our treatment of Alzheimer’s disease, they are not screening tools used for healthy people, nor does a positive result automatically mean someone has Alzheimer’s disease. They are intended to be used as a tool alongside a patient’s symptoms, medical history, and other clinical information. The rapid progress in one year is encouraging… as we have moved from the first FDA-cleared Alzheimer’s blood test to four different approaches for helping physicians uncover what may be happening inside the brain. For patients and families searching for answers and researchers working toward earlier detection/better treatments, this represents meaningful progress!

Dementia Digest is an educational resource from Clear Thoughts Foundation and is not intended to provide medical advice. Patients should speak with their healthcare providers and physicians regarding these test options.