Experts say 2 per cent of people receive a diagnosis of Alzheimer's using a lumbar puncture or PET scan. However, there are not enough PET scanners to screen for the disease at the rate required, which means many people wait years for a diagnosis.

Researchers will now study whether the result stands in populations in the real world, including clinics where people visit with concerns about their memory.

If it proves successful, experts say the test may be widely available in three to five years.

Dr Richard Oakley, associate director of research and innovation at the Alzheimer's Society, said: "This study is a hugely welcome step in the right direction as it shows that blood tests can be just as accurate as more invasive and expensive tests at predicting if someone has features of Alzheimer's disease in their brain.

"Furthermore, it suggests results from these tests could be clear enough to not require further follow-up investigations for some people living with Alzheimer's disease, which could speed up the diagnosis pathway significantly in future.

"However, we still need to see more research across different communities to understand how effective these blood tests are across everyone who lives with Alzheimer's disease."

Dr Sheona Scales, director of research at Alzheimer's Research UK, said the results suggest the new test was superior to other tests under development.

“This adds to a growing body of evidence that this particular test has huge potential to revolutionise diagnosis for people with suspected Alzheimer's,” she said.

But Dr Scales added that a clearer picture is needed of how these types of blood tests perform day-to-day in real-world healthcare systems.

David Curtis, honorary professor at the Genetics Institute at University College London, said: “Everybody over 50 could be routinely screened every few years, in much the same way as they are now screened for high cholesterol.

“It is possible that currently available treatments for Alzheimer's disease would work better in those diagnosed early in this way.

“However, I think the real hope is that better treatments can also be developed.

“The combination of a simple screening test with an effective treatment for Alzheimer's disease would have a dramatic impact for individuals and for society.”