A simple blood test is being developed that can predict the onset of Alzheimer's disease in people with poor memory.
British scientists have identified a set of protein biomarkers that appear to show if a person is likely to be diagnosed with the condition.
They hope further work will lead to a test that can single out high risk patients who can be targeted with early treatment.
Professor Paul Morgan, from the University of Cardiff, said: "Our research proves that it is possible to predict whether or not an individual with mild memory problems is likely to develop Alzheimer's disease over the next few years.
"We hope to build on this in order to develop a simple blood test that can predict the likelihood of developing Alzheimer's disease in older people with mild, and possibly innocent, memory impairment."
The team, including scientists from Cardiff, King's College London, and Oxford University, studied blood from 292 people with early signs of memory loss but who did not meet the diagnostic criteria for Alzheimer's.
The researchers, funded by the Alzheimer's Society charity, focused on proteins in the blood linked to an immune response known to drive inflammation and implicated in brain conditions.
When participants were re-assessed a year later, about a quarter had progressed to develop Alzheimer's disease. In those patients, there was a marked difference in the levels of three of the proteins measured.
The proteins predicted Alzheimer's onset with an accuracy of 85%.
Prof Morgan added: "Alzheimer's disease affects around 520,000 people in the UK and this number is continually growing as the population ages. As such it is important that we find new ways to diagnose the disease early, giving us a chance to investigate and instigate new treatments before irreversible damage is done."
The findings, published in the Journal of Alzheimer's Disease, lay the foundations for a much larger biomarker study funded by the Wellcome Trust and involving several UK universities and pharmaceutical companies.