FDA clears the first blood test to help diagnose Alzheimer's disease

On 16 May 2025 the FDA cleared for marketing in the US the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio, made by Fujirebio. It is the first FDA-cleared blood test to help diagnose Alzheimer's disease. It is intended for adults aged 55 and over with signs and symptoms of cognitive decline who are being assessed in a specialist setting.

How it works

The test measures two proteins in plasma, pTau217 and β-amyloid 1-42, and calculates the ratio between them. The ratio is linked to the presence of amyloid plaques in the brain, one of the hallmark changes of Alzheimer's disease. Until now, these plaques were confirmed with an amyloid PET scan or by analysing cerebrospinal fluid obtained through a lumbar puncture.

What the data showed

The FDA reviewed 499 plasma samples from adults with cognitive impairment. Of the positive results, 91.7% were confirmed by PET or cerebrospinal fluid testing, and of the negative results, 97.3% were confirmed negative. Fewer than 20% of patients received an indeterminate result that requires further testing.

What it means for patients

The FDA stresses that the test is not meant for screening people without symptoms and does not make a diagnosis on its own: the result must be interpreted by a doctor together with other clinical information. False-positive and false-negative results remain possible and can lead to unnecessary treatment or a delayed correct diagnosis.

Other tests have followed. In October 2025 the FDA cleared Roche's Elecsys pTau181 test for primary care, as an aid to identify patients who are unlikely to have Alzheimer's-related amyloid changes; Roche said the test also carries a CE mark in Europe. In May 2026 Fujirebio obtained a CE certificate under the EU in vitro diagnostic regulation for its Lumipulse G pTau 217 plasma test.

What we don't know yet

A CE mark allows a test to be sold in the EU, but availability depends on laboratories in each country. It remains to be seen how well these tests perform in everyday practice and how they will fit into the diagnostic pathway. If you or someone close to you has memory problems, ask a neurologist whether such a test would be useful in your case.