The first signs of Alzheimer’s disease are already advanced. So tests have to start far in advance. A new blood test can make the disease process visible to researchers.

“We can measure how the loss of nerve cells in the brain progresses, which is very important to test drugs and to see if you can stop the disease,” said Mathias Jucker of the German Center for Neurodegenerative Diseases (DZNE) at the site Tübingen. He has led an international study on a blood test for Alzheimer ‘s.

Irrevocable removal

In Alzheimer’s brain cells die gradually. Then they get into the blood. There, however, they are mined quite quickly and are no longer detectable. “An exception, however, is a small piece of a so-called neurofilament, which is amazingly resistant to degradation,” says Jucker.  

The scientists involved in the study were able to show that filaments accumulate in the blood long before the first clinical symptoms appear – ie already in the so-called preclinical phase. “We found out that the absolute value of neurofilaments is not important,” says Jucker. “The deciding factor is the change in filament concentration over time, so if the values ​​go up, it’s a sign that nerve cell loss is progressing.” 

Germany Science Research Medicine Researchers see Alzheimer's as a brain development disorder (picture alliance / dpa)

In Alzheimer’s brain cells die gradually

In one case, researchers used filaments to make predictions about brain mass loss and cognitive impairment. “Two years later, the changes actually happened,” says Jucker. “In Alzheimer’s, the loss of brain mass increases over time and ultimately leads to dementia.”

Suitable subjects

It has been found that the change in filament concentration and degradation of brain tissue are closely related. The filaments proved to be good biomarkers, ie indicators of biological processes. 

The researchers have studied people who have genetic changes and in which the Alzheimer’s disease already emerges relatively early, and not only at an advanced age.

About one percent of all Alzheimer’s sufferers belong to this rare group of people. She was ideal for conducting the study. In the subjects who were not genetically biased, the concentration of neurofilaments hardly changed and remained low.

The concentration of neurofilaments was increased in the pre-stressed persons. Over time, this concentration continued to increase, a particular region in the brain shrank. It is the region that is responsible for the memory functions. 

Icon image Gehrin Waves (Fotolia / Andrea Danti)

A research goal: to detect Alzheimer’s disease before the first symptoms appear

A total of 405 people were involved in the study. At regular intervals, Jucker and his colleagues examined each year whether and to what extent the value of neurofilaments in the blood went up. The data was collected and evaluated. The researchers found that there were significant changes in the blood up to 16 years before the calculated onset of dementia symptoms.

Decisive here was the temporal development of the filament concentration. It allows, so Jucker, predictions about the further course of the disease. The changes in neurofilament concentration accurately reflect neuronal degradation.

The researchers were thus able to predict how the brain would develop in the following years. “That way we can decide for each test subject whether it will still take fifteen years, if it will take another ten years, five or thirty years until the first symptoms appear,” explains Jucker. 

More important for research than for Alzheimer’s diagnosis

Not only in Alzheimer’s, but also in the course of further neurodegenerative diseases, it comes in the blood to the enrichment of neurofilaments. Thus, the test is only conditionally suitable for the diagnosis of Alzheimer’s. “The test is a very accurate indicator of disease progression, making it an excellent tool to explore new Alzheimer’s therapies in clinical trials,” said Jucker.

For example, the test makes research on Alzheimer’s disease easier because regular brain scans or other complicated imaging procedures in subjects no longer need to be performed as often.

In addition, unpleasant liquor tests are eliminated. The doctor removes nerve water from the spinal canal.

In general, volunteer study participants play an enormously important role in the work of Alzheimer’s researchers. “Without such subjects, without families willing to participate, our research results would never have been there,” says Jucker. Also in all further investigations, the researchers are dependent on test persons. Only then can they find out which other neurodegenerative diseases the blood test can be used for. 

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