A ''striking'' discovery by University of Otago researchers could pave the way for Alzheimer's to be diagnosed by a simple blood test.

The researchers have discovered a promising new marker among a small number of molecules, within a larger class of molecules called microRNA.

The marker molecules, found both in the human brain and blood, were ‘‘exceptionally good'' at detecting Alzheimer's, the researchers said.

A member of the Otago team, biochemist Prof Warren Tate, said Health Research Council programme funding had been crucial in gaining the ‘‘promising'' diagnostic results.

And researchers were seeking further funding, which would be critical in continuing the work.

Further research is needed to confirm and further clarify aspects of the earlier testing work, and, if the results can be confirmed and further clarified, it is understood that a blood test could becomeavailable about five years after that.

Prof Tate, a RNA biologist in the Otago team, said Otago researchers were also at a ‘‘promising and exciting stage'' in their hunt for new ways to treat Alzheimer's.

These other results would not be available until later this year, and important groundwork still had to be done before a clinical trial for a therapy was possible, he said.

Blood plasma microRNA had previously been shown to reflect various disease processes, and specific microRNA were linked to neurological diseases. This led Dr Joanna Williams, a senior lecturer in anatomy at Otago University, to suggest that blood microRNA levels may reflect changes in the brain.

Dr Joanna Williams led the screening of microRNA in the study participants' blood samples, supported by a member of her team, Diane Guevremont.

The specific set of blood microRNA markers identified by the Otago researchers can detect Alzheimer's correctly 86% of the time.

The proposed new test could have many advantages, including being ‘‘quick and easy to administer, relatively inexpensive and readily available'', she said.

Some other markers of early Alzheimer's had been previously known, but related testing involved costly or invasive and more time-consuming procedures that could not be used in routine clinical practice, she said.

If a GP took a blood sample from a patient starting to experience memory loss, researchers would analyse the blood and see its microRNA compared with ‘‘established patterns''.

Study participants included about 50 Otago people whose diagnosis with Alzheimer's had been confirmed in Dunedin by consultant neurologist Dr Nicholas Cutfield and clinical psychologist Prof Bob Knight.

Another 50 study participants, with no signs of neurological disorders, acted as a ‘‘control'' group.

Researchers believe the finding is an important breakthrough that could also potentially help with diagnosis at the ‘‘very earliest stages'' of the disease.

The discovery was made as part of a $4.6 million Health Research Council of New Zealand programme grant, directed by Prof Cliff Abraham, looking into markers and therapeutic targets for Alzheimer's and other dementias, which now affect more than 50,000 New Zealanders.

Prof Abraham is co-director of Brain Research New Zealand-Rangahau Roro Aotearoa, a national centre of research excellence. The team's ultimate goal was to develop a blood test that could spot the disease early, before people showed any clinical signs, Prof Abraham said.

HRC chief executive Prof Kath McPherson said New Zealand had a growing ageing population, and there could be ‘‘an exponential increase in disorders like Alzheimer's'' unless something was done.

The Otago researchers had made ‘‘excellent progress'' towards identifying people at risk of Alzheimer's and other dementias, she said.

john.gibb@odt.co.nz