Canadian and U.S. researchers say they have developed a relatively simple blood test that can detect Alzheimer's disease well before patients show advanced signs of the mind-destroying disorder.
Until now, there has been no diagnostic test that is both definitive and easy to use. In fact, a postmortem analysis of brain tissue has been the only way to confirm that a patient suffered from Alzheimer's and not another form of dementia.
The new test works by subjecting a blood sample to a chemical reaction known as oxidation. When blood samples from healthy individuals are put through this process, they generate relatively high levels of a brain hormone called dehydroepiandrosterone, or DHEA. But samples from people with Alzheimer's disease produced little 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," said the lead researcher, Vassilios Papadopoulos, of McGill University Health Centre in Montreal.
"Our data suggest we are able to pick up mild to moderate Alzheimer's, which means quite early," he added.
Even so, the usefulness of such a test is still limited because there are currently no effective treatments for slowing down the advance of the disease. However, it could prove helpful in the development of potential therapies and in tracking the progression of the disease in individual patients.
For instance, the test could be used to monitor patients undergoing clinical trials of experimental drug treatments. If there are significant changes in DHEA levels of oxidized blood, it may be an indication the treatment is working.
Dr. Papadopoulos noted that more research must be carried out to prove the test is an effective screening tool. So far, it has been used on only a limited number of patients.
"Within one or two years, we should have clear-cut answers about whether this holds up in a large population of patients," he said.
Other scientific teams are also trying to produce reliable and non-invasive diagnostic tests for Alzheimer's disease, which currently afflicts 18-million people worldwide, including 500,000 Canadians.
"I think, at the end of the day, there won't be just one test, but there will be a battery of blood-based tests that will be complementary and provide a picture of the patient's condition," predicted Dr. Papadopoulos.
He, along with colleagues at Georgetown University in Washington and University of California, San Diego, published their test results in this month's issue of the Journal of Alzheimer's Disease.
The researchers have filed for a patent on the blood test. Their work was partly financed by the U.S. National Institutes of Health, and Samaritan Pharmaceuticals, which holds the rights to market the test.