The new test, from Fujirebio Diagnostics, Inc., identifies a sticky brain plaque, known as beta-amyloid, that is a key marker for Alzheimer’s. Previously, the only FDA-approved methods for detecting amyloid were invasive tests of spinal fluid or expensive PET scans.

This new test is the first blood test ever approved for diagnostics of the disease, according to a press release issued Friday by the FDA. People suffering from the Alzheimer's su