A blood test that could make it easier for family doctors to check whether memory problems are linked to Alzheimer’s disease has been cleared by the US Food and Drug Administration. Roche announced the decision for its Elecsys pTau217 test on Monday, August 24. The test was developed with Eli Lilly.
How the test works
The test measures a single protein in the blood, phosphorylated tau 217 (p-tau217), which rises when amyloid plaques, a hallmark of Alzheimer’s, build up in the brain. Results fall into one of three groups:
- Positive: a high likelihood of amyloid pathology.
- Negative: a low likelihood, helping doctors rule Alzheimer’s out.
- Intermediate: confirmatory testing, such as a PET scan or spinal fluid test, is recommended.
The same two cut-off values apply in primary care and in specialist clinics, which Roche says makes the test simpler to use outside memory centres. It can run on the company’s existing laboratory analysers, more than 4,500 of which are installed across the United States.
Who it is for
The clearance covers adults aged 55 and older who already show signs, symptoms or complaints of cognitive decline. It is not a screening tool for healthy people, and it is not a stand-alone diagnosis: doctors must interpret it alongside a clinical assessment. The FDA has not established its value for predicting future dementia or for tracking treatment.
How it differs from last year’s test
In May 2025 the FDA cleared the first Alzheimer’s blood test, made by Fujirebio, which uses a ratio of two proteins. Roche’s version relies on one biomarker, which the company says gives a clearer rule-in or rule-out answer.
Why it matters
Diagnosing Alzheimer’s has traditionally required expensive brain scans or a lumbar puncture, so many people wait months or are never formally assessed. A routine blood draw at a GP surgery could shorten that path and help identify people who may be eligible for newer amyloid-targeting drugs, which work best early in the disease.
Specialists caution that blood tests work best in people who already have symptoms, and that results should come with counselling. As Lilly’s neuroscience chief Carole Ho put it, a timely diagnosis is “the first and most critical step toward meaningful care.”