A blood test could help Alzheimer's patients
Their experiments in mice seem to be able to accurately detect the amount of a body protein called amyloid in the brain.
The protein has been strongly linked to the development of Alzheimer's as it clumps together, and forms "plaques" in the organ, killing brain cells.
By the time symptoms of Alzheimer's dementia appear, it is likely that the plaques have been forming in the brain for some time - perhaps years - undetected.
The study, published in the journal Science, was carried out by researchers at the Washington University School of Medicine in St Louis.
Some testers have measured the level of amyloid proteins in the blood, and tried to use this as a guide to the amyloid levels in the brain, but this has not proved particularly reliable.
Fine-tuned test
The US team looked at mice with a particular genetic mutation which made it inevitable they would develop amyloid plaques - although to different degrees.
Afterwards, within a few minutes, blood levels of the protein appeared to correlate accurately to the level of plaques formed in the brains of the mice.
Associate Professor David Holtzman, one of the research team, said: "This has obvious implications for developing a similar blood test for brain amyloid load in humans.
"Though we will not be able to detect risk in someone who has not begun to accumulate amyloid, we hope to predict the disease well before the symptoms appear.
"Such a test could distinguish individuals suffering from dementia caused by Alzheimer's from those with other types of dementia, and may help us evaluate an individual's response to particular medical therapies."
Planning ahead
Dr Simon Lovestone, from the Institute of Psychiatry at King's College London, said that even if treatments for Alzheimer's were not available, being able to receive a quick diagnosis was important to patients.
He said: "One of the most important things is that they get an early diagnosis - they can start putting things in order and preparing for what lies ahead."
However, he said that although a treatment would not be available for at least 10 years, he was hopeful that trials of potential medication would be successful.