The U.S. Food and Drug Administration (FDA) has approved the Elecsys pTau181 blood test. It’s the first test primary care doctors can use to help rule out Alzheimer’s disease with 97.9 percent accuracy.

The new test offers a new, highly reliable way for people experiencing memory and thinking problems to get answers — and avoid unnecessary, invasive testing.

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“This is another important step toward expanding access to Alzheimer’s disease diagnostic tools,” said Joanne Pike, DrPH, Alzheimer’s Association president and chief executive officer. “By using a ‘rule out’ initial tool in the primary care setting, we can help people who are not living with Alzheimer’s get to the root of their cognitive symptoms faster, while ensuring those who may have the disease are referred for appropriate testing, definitive diagnosis, and early treatment.”

How the Blood Test Works

The Elecsys pTau181 blood test measures a protein in the blood called phosphorylated tau 181 (pTau181). Changes in this protein are linked to the buildup of amyloid plaques and tau tangles in the brain, which are key signs of Alzheimer’s disease. The test is approved for adults aged 55 and older who are experiencing signs of cognitive decline.

The main role of this test is to help rule out Alzheimer’s-related amyloid pathology. If the test result is negative, it is very likely that Alzheimer’s is not the cause of the cognitive symptoms.

“It is important to understand this test is designed to rule out the presence of amyloid plaques. It is not a test that will give an Alzheimer’s disease diagnosis, nor is it a standalone tool for detection,” Pike said.

The FDA based its approval on a study of 312 people reflecting a population similar to those seen in primary care.

What This Means for Alzheimer’s Diagnosis

The FDA approval of the Elecsys pTau181 blood test marks a major step toward making Alzheimer’s diagnosis more accessible and less invasive. Until now, blood-based tests for Alzheimer’s were mostly available only in research or specialized clinics.

Among them is the Lumipulse G pTau217/Beta-Amyloid 1-42 Plasma Ratio test, approved by the FDA earlier this year. The Lumipulse test works by measuring the ratio of two proteins, pTau217 and beta-amyloid 1-42, in the blood. However, the Lumipulse test is mainly used in specialized laboratory settings and is intended for people who already have signs and symptoms of cognitive decline.

With the Elecsys pTau181, primary care doctors can use this test to help rule out Alzheimer’s for many people, preventing unnecessary worry, testing, and specialist visits.

Getting an early and accurate diagnosis of Alzheimer’s disease is important. It can help you and your loved ones plan for the future, start treatment sooner, and access support services. If you or a loved one is experiencing memory or thinking problems, talk with your doctor about what tests may be right for you.

Learn more about Alzheimer’s diagnosis.

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