Researchers in Montreal say they may have uncovered the method for creating a blood test that could diagnose Alzheimer's disease in its early stages, when early treatment could help slow disease progression.
The research, published in this month's issue of the Journal of Alzheimer's Disease, shows how searching for a precursor of a biochemical marker called dehydroepiandrosterone (DHEA), appears to identify people with early Alzheimer's.
DHEA is a brain hormone that should be present at high levels in the brain where it provides a wide range of roles in brain function. Patients with early Alzheimer's disease seem to have abnormally low levels of the hormone in their blood.
The test involves performing a chemical reaction, called oxidation, on a blood sample. Oxidation causes production of DHEA if an as-yet-unidentifed DHEA precursor is present in the blood.
The study found that in non-Alzheimer's patients, the oxidation process produced the hormone, but the blood from Alzheimer's patients did not produce DHEA.
In a telephone interview with CTV News, the test's developer, Dr. Vassilios Papadopoulos, director of the McGill University Health Centre Research Institute, said that the test was used on 83 patients, half with early-stage Alzheimer's; the rest were healthy controls.
"All the patients with Alzheimer's disease tested positive. All the normal patients were negative," he said.
Papadopoulos called the results "exciting" because not only could the test one day be used to identify patients early -- a test that has so far eluded researchers -- but it might help doctors monitor the effectiveness of drug treatments.
"Until now, there has been no definitive diagnostic tool for Alzheimer's, other than postmortem analysis of brain tissue," said Papadopoulos.
Currently, diagnosing Alzheimer's disease relies on an evaluating family history and symptoms. Absolute confirmation can only be conducted through post-mortem brain analysis.
Papadopoulos has collected about 400 more blood samples from other Alzheimer's patients. His team will also recruit samples from an equal number of cognitively healthy control subjects for a larger study to see if they can replicate the initial results. Further tests might also be able to measure the effects of various medications on the progression of the disease.
The study was co-sponsored by the U.S National Institutes of Health and the manufacturer working to develop the blood test, Samaritan Pharmaceuticals.
