Blood test to spot Alzheimer’s goes on sale

A company has started selling the first blood test to help diagnose Alzheimer’s disease, a leap for the field. It also raises concern about the accuracy of such life-altering news. Independent experts are leery because key test results have not been published and the test has not been approved by the US FDA. But they agree that a simple test that can be done in a doctor’s office has long been needed. More than 5 million people in the US and millions more around the world have Alzheimer’s. To be diagnosed with it, people must have symptoms such as memory loss plus evidence of a buildup of a protein called beta-amyloid in the brain. The best way now to measure the protein is a costly PET brain scan. That means most people don’t get one. The blood test from C2N Diagnostics of St Louis aims to fill that gap.

The test measures two types of amyloid particles plus various forms of a protein that reveal whether someone has a gene that raises risk for the disease. These factors are combined in a formula that includes age, and patients are given a score suggesting low, medium or high likelihood of having amyloid buildup in the brain.