Alzheimer: blood test diagnosis

A blood test for a protein could identify people in the early stages of Alzheimer's disease a decade or more before symptoms, such as a decline in memory and thinking, emerge.

This was what an international group of scientists concluded after evaluating the simple test that used blood samples from people with a rare form of Alzheimer's disease that they had inherited.

The team included researchers from Washington University School of Medicine in St. Louis, MO and the German Center for Neurodegenerative Diseases in Tübingen, Germany.

The test looks for changes in levels of the neurofilament light chain (NfL) protein. The protein normally resides inside brain cells, or neurons, as part of their internal skeleton.

However, damaged and dying cells can leak NfL into surrounding cerebrospinal fluid. The protein then travels from the fluid into the bloodstream.

Now, in a Nature Medicine paper about the recent study, the authors report how they demonstrated that NfL levels in spinal fluid correlated with levels in blood and "are elevated at the presymptomatic stages of familial Alzheimer's disease."

"This could be," says co-first study author Stephanie A. Schultz, who is a graduate student at Washington University, "a good preclinical biomarker to identify those who will go on to develop clinical symptoms."

The researchers suggest that the quick and inexpensive method could one day also test for other conditions involving brain damage, such as traumatic brain injury, multiple sclerosis, and stroke.

In the new research, the team studied a rare form that has the name dominantly inherited Alzheimer's disease (DIAD), or autosomal dominant Alzheimer's disease.

The data for the study came from the Dominantly Inherited Alzheimer's Network (DIAN), which is an international consortium that Washington University leads. The aim of the network is to investigate the causes of Alzheimer's disease.

DIAD arises from a mutation in one or more of three genes: PSEN1, PSEN2, or APP.

People with DIAD typically experience memory loss and other symptoms of dementia in their 30s, 40s, and 50s.

The researchers chose to study people with DIAD because the earlier onset of the disease gives a longer timespan over which to investigate brain changes before cognitive symptoms emerge.

Results from the brain scans were in line with the changes in NfL levels.

The rate of increase in the protein matched the rate of thinning and shrinkage in the brain's precuneus, which has a role in memory.

Read more on https://doi.org/10.1038/s41591-018-0304-3