In a study published Tuesday in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, researchers said they found a set of 10 proteins in the blood that seem predictive.
"We have identified 10 plasma proteins strongly associated with disease severity and disease progression," Simon Lovestone, a neuroscience professor at Oxford University in the U.K., and his co-authors concluded.
Lovestone said he thinks the real use will be in better clinical trials. Clinical trials are now done in people with established Alzheimer's disease, when it may be too late for a drug to work.
Over the past 15 years, more than 100 experimental Alzheimer's drugs have failed to prevent or reverse the disease.
The idea behind a predictive test would be to guide the selection of subjects for drug trials to show whether an experimental drugs works.
But clinically, the test's accuracy rate "does not mean that a blood test for dementia is just around the corner," cautioned James Pickett, head of research at the Alzheimer's Society in the U.K.
"These 10 proteins can predict conversion to dementia with less than 90 per cent accuracy, meaning one in 10 people would get an incorrect result," he said. "Accuracy would need to be improved before it could be a useful diagnostic test."
Any potential diagnostic test would also have be backed up with scans and memory tests.
Previous studies have used PET brain scans and tests of lumbar fluid to try to distinguish the onset of dementia from people with a less severe condition known as mild cognitive impairment (MCI). The tests are expensive and invasive.
For the latest study, researchers tested blood samples from 1,148 people in the U.K. and Canada — 476 with Alzheimer's, 220 with mild cognitive impairment and 452 elderly controls without dementia. They were analyzed for 26 proteins previously found to be linked with Alzheimer's.
The team found 16 of these 26 proteins to be strongly associated with brain shrinkage in either MCI or Alzheimer's.
In a second round of tests, the researchers checked which proteins could predict which subjects would progress from MCI to Alzheimer's.
Lovetone has filed a patent with Proteome Sciences related to the findings. Several authors are employees of Proteome and one is an employee of pharmacautical company Glaxo Smith-Kline.