A British study has identified blood proteins that appear in patients subsequently diagnosed with Alzheimer's, raising hopes of a test that could help the search for a cure.

There is currently no cure for the brain-wasting disease, the most common form of dementia, which Alzheimer's Disease International estimates affects 44 million people worldwide, a figure set to triple by 2050.

A test to diagnose the disease early on would allow researchers to monitor patients before they develop advanced symptoms, potentially helping the search for a cure.

The study published in the journal Alzheimer's & Dementia monitored 220 patients with mild cognitive impairment.

The researchers identified 10 proteins that were present in the blood of 87 percent of those in the group who went on to be diagnosed with Alzheimer's within a year.

"Many of our drug trials fail because by the time patients are given the drugs, the brain has already been too severely affected," said Oxford University neuroscience professor Simon Lovestone, who led the study in King's College London.

"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. The next step will be to validate our findings in further sample sets."

James Pickett, head of research at the Alzheimer's Society, warned that as accuracy was under 90 percent, it would have to be improved before such a test would be useful.

"Only through further research will we find answers to the biggest questions around dementia, so we will watch the progress of this study with interest," Pickett said.