WELLINGTON, April 5 -- New Zealand scientists said Tuesday they have discovered a promising new market that could lead to the diagnosis of Alzheimer's disease with a simple blood test.

Researchers at Otago University discovered that a small number of a large class of molecules called microRNA - found in both the human brain and blood - were exceptionally good at detecting Alzheimer's disease, a debilitating form of dementia.

Previously, blood plasma microRNA had been shown to reflect various disease processes, and specific microRNA were linked to neurological diseases, prompting researcher Dr Joanna Williams to suggest that blood microRNA levels might reflect changes in the brain.

The specific set of blood microRNA that the Otago researchers had identified could detect Alzheimer's disease correctly 86 percent of the time.

The exact identities of the diagnostic molecules were still secret, but the researchers believed the finding was an important breakthrough that had the potential to help with diagnosis at the very earliest stages of the disease.

"Although there are other known markers of early Alzheimer's disease, such as an accumulation of the toxic protein beta amyloid in the brain, testing for these involves expensive or invasive procedures that can't be used in routine clinical practice," Williams said in a statement.

A blood test to diagnose Alzheimer's would be quick and easy to administer, relatively inexpensive, and readily available.

"We know that the levels of these microRNA differ in people who have Alzheimer's and people who don't. So if a GP took a blood sample from a patient who was beginning to show symptoms of memory loss, what we'd do is analyze that blood and see how that patient's pattern of microRNA compares against established patterns."

The team was also working on a blood test to predict whether a person without symptoms was likely to get Alzheimer's in the future.