In order to increase the number of correctly identified Alzheimer's cases and to reduce the number of false positive diagnoses, the researchers introduced the two-tier diagnostic method.
Scientists have developed a simple blood test that may help detect Alzheimer’s disease eight years before the first clinical symptoms occur. Using current techniques, Alzheimer’s disease, the most frequent cause of dementia, can only be detected once the typical plaques have formed in the brain, said researchers from Ruhr-Universitat Bochum (RUB) in Germany. At this point, therapy seems no longer possible, they said. However, the first changes caused by Alzheimer’s take place on the protein level up to 20 years earlier.
A two-tier method, described in the journal Alzheimer’s and Dementia: Diagnosis, Assessment and Disease Monitoring, can help detect the disease at a much earlier stage.”This has paved the way for early-stage therapy approaches, where the as yet inefficient drugs on which we had pinned our hopes may prove effective,” said Professor Klaus Gerwert from RUB.
In Alzheimer’s patients, the amyloid beta protein folds incorrectly due to pathological changes long before the first symptoms occur. Researchers successfully diagnosed this misfolding using a simple blood test. As a result, the disease can be detected about eight years before the first clinical symptoms occur, they said.
However, the test was not suitable for clinical applications, according to the researchers. It detected 71 per cent of Alzheimer’s cases in symptomless stages, but provided false positive diagnoses for nine per cent of the study participants, they noted. In order to increase the number of correctly identified Alzheimer’s cases and to reduce the number of false positive diagnoses, the researchers introduced the two-tier diagnostic method.
They used the original blood test to identify high-risk individuals. They added a dementia-specific biomarker, tau protein, to run further tests with those test participants whose Alzheimer’s diagnosis was positive in the first step.
If both biomarkers show a positive result, there is a high likelihood of Alzheimer’s disease, researchers said. “Through the combination of both analyses, 87 of 100 Alzheimer’s patients were correctly identified in our study,” said Gerwert.”And we reduced the number of false positive diagnoses in healthy subjects to three of 100.”The second analysis is carried out in cerebrospinal fluid that is extracted from the spinal cord,” he said.
“Now, new clinical studies with test participants in very early stages of the disease can be launched,” said Gerwert. He is hoping that the existing therapeutic antibodies will still have an effect. “Once amyloid plaques have formed, it seems that the disease can no longer be treated,” said Andreas Nabers, head of the research group and co-developer of the Alzheimer’s. The blood test has been upgraded to a fully automated process. “The sensor is easy to use, robust when it comes to fluctuation in concentration of biomarkers, and standardised,” said Nabers.