The United States approves the first blood test that can diagnose Alzheimer's disease.

 US health authorities approved the first blood test to diagnose Alzheimer's disease on Friday, potentially enabling patients to start taking medications earlier to slow the progression of this neurodegenerative disease.

The test, developed by Fujirebio Diagnostics, measures the levels of two proteins in the blood. This level is associated with the presence of beta-amyloid plaques in the brain, a hallmark of Alzheimer's disease, and previously could only be detected through brain scans or spinal fluid analysis.

Marty Makary of the US Food and Drug Administration noted, "Alzheimer's disease affects a very large number of people, more than breast cancer and prostate cancer combined."

He added, "10 percent of those aged 65 and older have Alzheimer's, and that number is expected to double by 2050," expressing hope that "new medical products like this test will help them."

Two currently available drugs for Alzheimer's disease, lecanemab and donanemab, target amyloid plaques and slow cognitive decline to a limited extent, but they do not provide a cure.

Proponents of these drugs, including many neurologists, believe they can give patients a few extra months of independence and are more effective if administered early.

Blood test results in clinical trials were largely similar to those obtained from PET brain scans and cerebrospinal fluid analysis.

Michelle Tarver, of the Centers for Devices and Radiological Health at the US Department of Health and Human Services, said the approval of the new test "marks a significant milestone for the diagnosis of Alzheimer's disease, making it easier and more accessible to patients in the United States at an earlier stage of the disease."

The test has been approved for clinical use in patients with signs of cognitive decline, with interpretation of the results taking into account other clinical information.

Alzheimer's disease is the most common form of dementia. The condition deteriorates over time, gradually leading to loss of memory and independence.