A simple blood test can find signs of brain damage in people who are on the path to getting Alzheimer’s disease—even before they show signs of confusion and memory loss, according to a new study. The findings, published in Nature Medicine, may quickly and inexpensively identify brain damage in people with not just Alzheimer’s disease but other neurodegenerative conditions such as multiple sclerosis, TBI or stroke. The test finds neurofilament light chain, a kind of protein. When brain neurons are damaged or dying, the protein leaks out into the cerebrospinal fluid that bathes the brain and spinal cord and from there, into the bloodstream. Finding high levels of the protein in a person’s cerebrospinal fluid has been shown to provide strong evidence that some of their brain cells have been damaged. But getting cerebrospinal fluid requires a spinal tap, which many people are reluctant to get. Researchers studied whether levels of the protein in blood also reflect neurological damage.
The researchers studied more than 400 people participating in the DIAN study, 247 who carry an early-onset genetic variant and 162 of their unaffected relatives. In those with the faulty gene variant, protein levels were higher at baseline and rose over time. In contrast, protein levels were low and largely steady in people with the healthy form of the gene. This difference was detectable 16 years before cognitive symptoms were expected to arise.
A commercial kit—very similar to the one used by the authors—is available to test for protein levels in the blood, but it has not been approved by the FDA to diagnose or predict an individual’s risk of brain damage. Before such a test can be used for individual patients with Alzheimer’s or any other neurodegenerative condition, researchers will need to determine how much protein in the blood is too much, and how quickly protein levels can rise before it becomes a cause for concern.