Adapted from Stanford University Medical Center
One of the most distressing aspects of Alzheimer's disease is the difficulty in determining whether mild memory problems are the beginning of an inevitable mental decline. Researchers at the Stanford University School of Medicine have developed a blood test that is a step toward giving people an answer two to six years in advance of the onset of the disease.
The test identifies changes in a handful of proteins in blood plasma that cells use to convey messages to one another. The research team discovered a connection between shifts in the cells' dialog and the changes in the brain accompanying Alzheimer's. They found that the blood test could indicate who had Alzheimer's with 90 percent agreement with clinical diagnoses, and could predict the onset of Alzheimer's two to six years before symptoms appeared.
"Just as a psychiatrist can conclude a lot of things by listening to the words of a patient, so by 'listening' to different proteins we are measuring whether something is going wrong in the cells," said Tony Wyss-Coray, PhD, associate professor of neurology and neurological sciences and senior author of the study.
"It's not that the cells are using new words when something goes wrong," said Wyss-Coray. "It's just that some words are much stronger and some are much weaker; the chatter has a different tone."
The study will appear in the October 15, 2007 advance online edition of Nature Medicine.
"I really think it has enormous potential," said Lennart Mucke, MD, director and senior investigator of the Gladstone Institute of Neurological Disease at the University of California-San Francisco, who did not participate in the study. "Most researchers in this field agree that there is an urgent need for better lab tests for Alzheimer's disease, and this study has addressed this need admirably."
Listening to cells' messages may not only lead to the first noninvasive diagnostic test for Alzheimer's; it could also lead to similar discoveries about other disorders by focusing on what cells use to talk to each other, said Wyss-Coray, who is part of the Geriatric Research, Education and Clinical Center at the Veterans Affairs Palo Alto Health Care System.
Currently, the clinical diagnosis for Alzheimer's is one of exclusion—by testing for other causes of memory loss and cognitive declines, such as stroke, tumors and alcoholism. If those conditions are eliminated as causes of memory loss, what remains is Alzheimer's, which is the most common cause of dementia. Even the clinical diagnosis is imperfect, and the only definitive diagnosis is by brain autopsy after a person has died.
The Alzheimer's blood test, will be developed initially for research labs and, if confirmed as reliable, eventually as a clinical diagnostic test upon regulatory approval.