Blood test for Alzheimer's: Study identifies procedure that detects early stages

This research, published in the month's issue of the Journal of Alzheimer's Disease, has implications for the millions of sufferers worldwide.

"Until now, there has been no definitive diagnostic tool for Alzheimer's, other than postmortem analysis of brain tissue," says senior author Dr. Vassilios Papadopoulos, director of the MUHC Research Institute. "Our clinical study shows that a non-invasive blood test, based on a biochemical process, may be successfully used to diagnose Alzheimer's at an early stage and differentiate it from other types of dementia."

The biochemistry behind the test

Papadopoulos and colleagues based the Alzheimer's blood test on the production of a brain hormone called dehydroepiandrosterone (DHEA). This hormone is present at high levels in the brain where it has a wide range of biological effects.

The researchers were able to promote the production of DHEA, using a chemical process called oxidation, in blood taken from non-Alzheimer's patients. However, oxidation of blood from Alzheimer's patients did not result in an increase of DHEA.

"There is a clear correlation between the lack of ability to produce DHEA through oxidation in the blood and the degree of cognitive impairment found in Alzheimer's disease," says Papadopoulos. "We demonstrated we could accurately and repetitively detect Alzheimer's disease, with small samples of blood. This test also allowed for differential diagnosis of early stages of Alzheimer's disease, suggesting this can be used as a test to diagnose the disease in its infancy."

Treatment implications

"There are many candidate disease-modifying therapies that target the underlying development of Alzheimer's disease, which are in clinical trials," adds Papadopoulos. "However, the implementation of any therapy is dependant on the reliability of the diagnosis."

Currently the diagnosis of Alzheimer's follows the sequence of family history, information, mental assessment and the physical exam, focusing on neurological signs.

"An accurate, easy and specific non-invasive biochemical test that correlates with clinical findings is vital. We believe our results demonstrate that the DHEA-oxidation blood test can be used to diagnose Alzheimer's at a very early stage and monitor the effect of therapies and the evolution of the disease."

The study was authored by Georges Rammouz, Laurent Lecanu and Vassilios Papadopoulos from the MUHC Research Institute and McGill University; Paul Aisen from the University of California at San Diego.

This work was supported by funds from the National Institutes of Health and Samaritan Pharmaceuticals.