A blood test might be able to identify Alzheimer's disease long before there are symptoms of the brain-destroying disorder, say researchers who hope early knowledge can help in developing treatment.
In a study appearing today in the journal Science, researchers at Washington University School of Medicine in St. Louis say that injecting an antibody into mice causes a sudden flood in the bloodstream of a protein that forms neuron-destroying plaques in the brain.
The level of the protein, amyloid-beta, after the injection was an indication of the amount of plaque, said David Holtzman, a Washington University neurologist and co-author of the study.
He emphasized that although the technique works in a strain of mice that develop Alzheimer's, it is not known if the test would work in humans. Because the disease progresses so slowly, Holtzman said it would take at least five years of studies before the test's value could be proven in humans.
Holtzman said the study is a part of a major effort by Alzheimer's disease researchers to find a way to identify people who will develop the disease before they have obvious symptoms.
Alzheimer's can be proven only at autopsy, although some clinical tests can diagnose it to a high degree of accuracy after profound symptoms have appeared.
No proven effective drugs can cure or control the progression of Alzheimer's. Some studies have suggested that folic acid and cholesterol control drugs can be beneficial, but research is under way. Holtzman said that an early diagnostic test would enable doctors to identify patients who need treatment, allow tracking of the disease progression and help to test candidate drugs.
An estimated 4-million Americans have Alzheimer's disease, and the total is expected to grow to about 14-million by 2050.
Amyloid-beta is a normal substance in the body, but starting at about age 50 it can accumulate in plaques in the brain. These plaques are linked to the death of neurons, causing a gradual loss of memory and control of body function that leads to death.
Holtzman said the study in mice suggests that the blood test could identify the tendency to form amyloid-beta plaques at an early point in the disease.
Bill Thies, vice president for medical and scientific affairs of the Alzheimer's Association, said a blood test would be an important advance.
"We really do need a biological way to track the disease," he said. "If we had that, it would increase our ability to identify people and would greatly accelerate clinical trials" of candidate drugs.