The early stages of Alzheimer's disease are preceded by rising levels of amyloid-β in the brain. This may be due to impaired drainage of cerebrospinal fluid, chronic infection by persistent pathogens, or other mechanisms. Since amyloid-β can be exported from the brain into the bloodstream, and since there is a dynamic equilibrium between levels in the two locations, it is in principle possible for a blood test to identify those most at risk of developing Alzheimer's disease. Unfortunately developing the necessarily accuracy has proven challenging. Researchers here report on meaningful progress towards this goal, however, which is welcome news.
Currently, a major support in the diagnostics of Alzheimer's disease is the identification of abnormal accumulation of the substance beta-amyloid, which can be detected either in a spinal fluid sample or through brain imaging using a PET scanner. "These are expensive methods that are only available in specialist healthcare. In research, we have therefore long been searching for simpler diagnostic tools." In this study, the researchers investigated whether a simple blood test could identify people in whom beta-amyloid has started to accumulate in the brain, i.e. people with underlying Alzheimer's disease. Using a simple and precise method that the researchers think is suitable for clinical diagnostics and screening in primary healthcare, the researchers were able to identify beta-amyloid in the blood with a high degree of accuracy.
"Previous studies on methods using blood tests did not show particularly good results; it was only possible to see small differences between Alzheimer's patients and healthy elderly people. Only a year or so ago, researchers found methods using blood sample analysis that showed greater accuracy in detecting the presence of Alzheimer's disease. The difficulty so far is that they currently require advanced technology and are not available for use in today's clinical procedures."
The new results are based on studies of blood analyses collected from 842 people in Sweden (the Swedish BioFINDER study) and 237 people in Germany. The participants in the study are Alzheimer's patients with dementia, healthy elderly people and people with mild cognitive impairment. The method studied by the researchers is a fully automated technique which measures beta-amyloid in the blood, with high accuracy in identifying the protein accumulation. "The next step to confirm this simple method to reveal beta-amyloid through blood sample analysis is to test it in a larger population where the presence of underlying Alzheimer's is lower. We also need to test the technique in clinical settings, which we will do fairly soon in a major primary care study in Sweden. We hope that this will validate our results."