Scientists have identified a set of 10 blood proteins which can help predict the onset of Alzheimer's with 87 per cent accuracy.
The study, led by King's College London and UK proteomics company, Proteome Sciences plc, analysed over 1,000 individuals and is the largest of its kind to date.
There are currently no effective long-lasting drug treatments for Alzheimer's, and it is believed that many new clinical trials fail because drugs are given too late in the disease process.
A blood test could be used to identify patients in the early stages of memory loss for clinical trials to find drugs to halt the progression of the disease.
The researchers used data from three international studies.
Blood samples from a total of 1,148 individuals (476 with Alzheimer's disease; 220 with 'Mild Cognitive Impairment' (MCI) and 452 elderly controls without dementia) were analysed for 26 proteins previously shown to be associated with Alzheimer's disease.
A sub-group of 476 individuals across all three groups also had an MRI brain scan.
Researchers identified 16 of these 26 proteins to be strongly associated with brain shrinkage in either MCI or Alzheimer's.
They then ran a second series of tests to establish which of these proteins could predict the progression from MCI to Alzheimer's.
They identified a combination of 10 proteins capable of predicting whether individuals with MCI would develop Alzheimer's disease within a year, with an accuracy of 87 per cent.
Memory problems are very common, but the challenge is identifying who is likely to develop dementia. There are thousands of proteins in the blood, and this study is the culmination of many years' work identifying which ones are clinically relevant," Dr Abdul Hye, lead author of the study from the Institute of Psychiatry at King's, said.
"We now have a set of 10 proteins that can predict whether someone with early symptoms of memory loss, or mild cognitive impairment, will develop Alzheimer's disease within a year, with a high level of accuracy," said Hye.
"A simple blood test could help us identify patients at a much earlier stage to take part in new trials and hopefully develop treatments which could prevent the progression of the disease," Professor Simon Lovestone, senior author of the study from the University of Oxford, who led the work whilst at King's, said.
"The next step will be to validate our findings in further sample sets, to see if we can improve accuracy and reduce the risk of misdiagnosis, and to develop a reliable test suitable to be used by doctors," said Lovestone.
The study was published in the journal Alzheimer's & Dementia.