FDA Approves Alzheimer’s Blood Test

The U.S. Food and Drug Administration (FDA) has given marketing clearance to the Lumipulse G pTau217/ß-Amyloid 1-42 Plasma Ratio, a blood test to help diagnose Alzheimer’s disease for adults 55 and older who are showing signs and symptoms of the disease. It is the first test to be approved to aid in the early detection of the disease in the United States.

Approval was based on clinical trial data of plasma samples collected from 499 adults who were cognitively impaired. The samples were evaluated using the blood test, and the results were compared with the results from patients’ PET scans or separate testing using cerebrospinal fluid samples such as from spinal taps. Data showed that 91.7 percent of adults with positive results using the blood test had the presence of amyloid plaques confirmed by their PET scan or cerebrospinal fluid test, and 97.3 percent of people with negative results had a negative amyloid PET scan or cerebrospinal fluid test result.

The test works by measuring two proteins in blood plasma: pTau217 and beta-amyloid 1-42. A ratio of those proteins tends to correlate with the occurrence or absence of amyloid plaques in the brain, which are among the hallmarks of Alzheimer’s disease. It does not measure amyloid directly but can signal its presence. However, there remains no current single test to diagnose Alzheimer’s disease. Doctors primarily rely on a medical history, neurological exams, cognitive and functional evaluations, brain imaging, spinal fluid analysis and, more recently, blood tests.

According to FDA, the results of the newly cleared blood test must be assessed in conjunction with other clinical information from a patient. “Alzheimer’s disease impacts too many people, more than breast cancer and prostate cancer combined,” FDA Commissioner Martin Makary, MD, MPH, said. “Knowing that 10 percent of people aged 65 and older have Alzheimer’s, and that by 2050 that number is expected to double, I am hopeful that new medical products such as this one will help patients.”

The test — developed by Fujirebio Diagnostics Inc. — can help increase access to Alzheimer’s disease detection and reduce reliance on PET scans, a type of imaging that can reveal amyloid plaques in the brain but can be expensive, costing thousands of dollars without insurance.

The risks associated with the blood test are mainly the risk of a false positive or false negative test result.