October 29, 2025
The Food and Drug Administration has approved a new blood test to aid in the diagnosis of Alzheimer’s disease. It is intended for use by primary care doctors to help rule out Alzheimer’s disease as the cause of memory and thinking problems in adults 55 and older.
The test, known as Elecsys p Tau181, measures blood plasma levels of a modified form of the tau protein, which is a hallmark of Alzheimer’s disease. It was developed by the drug makers Roche and Eli Lilly. In a clinical trial of 312 participants, the Elecsys pTau181 test was correctly able to rule out Alzheimer’s disease 97.9 percent of the time. A negative test therefore strongly suggests that Alzheimer’s is unlikely the cause of a patient’s thinking and memory problems.
The newly approved Alzheimer’s test is the second such test to receive FDA approval. The first, known as the Lumipulse test, developed by Fujirebio Diagnostics, was approved earlier this year and measures levels of two different proteins: a different form of tau as well as beta-amyloid, another hallmark of Alzheimer’s.
Unlike the Lumipulse test, which is generally used in specialized care settings under the guidance of neurologists or other specialists, the Elecsys pTau181 test is intended for use in the primary care setting. A doctor who sees an older patient who is worried about cognitive changes might, for example, choose to administer the simple blood test in their office. A negative result might then encourage the doctor to do additional follow-up to look for other possible causes of memory problems, such as depression or anxiety, medication side effects or sleep disorders. Other causes of cognitive problems include infections, thyroid disorders or vitamin deficiencies.
A positive test result, on the other hand, does not mean you have Alzheimer’s disease. Patients who get a positive test result, as well as some who get a negative result, might be encouraged to see a neurologist or other specialist for additional follow-up. More definitive testing might include a possible spinal tap or brain scan which can detect signs of Alzheimer’s more directly.
The new test is not intended as a screening test for healthy individuals, so people who don’t have memory loss or other symptoms shouldn’t get tested. The test should become increasingly available in doctor’s offices in the coming months.
Neither of the newly approved blood tests are definitive, but they may provide an initial first step in helping to determine the root cause of thinking and memory problems in older adults. Additional Alzheimer’s blood tests are in development. Some target other measures, such as levels of inflammation in the brain.
As experience with the blood test grows and new tests become available, doctors may be able to offer more personalized treatments for individual patients with Alzheimer’s disease. By speeding up the diagnostic process, such tests could make it simpler for patients to access some of the newer Alzheimer’s drugs, which may offer the most benefit (albeit modest) when taken early in the course of the disease.
Anyone interested in the new blood tests should talk to their doctor for more information. This article is for informational purposes only and is not an endorsement of these tests by The Fisher Center Foundation or its affiliated scientists.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Food and Drug Administration, Roche
