LONDON, Aug 15 (Xinhua) -- A simple skin test could enable doctors to diagnose Alzheimer's disease in its very early stages preventing major brain damage, researchers say.

Researchers at the Blanchette Rockefeller Neurosciences Institute in Rockville, Maryland, the U.S., have identified chemical changes that distinguish early Alzheimer's from other neuro-degenerative disorders, the New Scientist magazine reported on Tuesday on its website.

While studying the inflammatory pathways that underpin Alzheimer's disease, Daniel Alkon and his colleague Tapan Khan found that the brain and skin cells of Alzheimer's patients responded differently to the inflammatory chemical bradykinin compared to tissue taken from patients with other dementias or neuro-degenerative diseases.

The chemical signal is produced in skin cells as well as brain tissue, which would make for a safe and convenient diagnostic test,the researchers said.

The ratio of activity of two related enzymes, ERK1 and ERK2, distinguished tissue taken from Alzheimer's patients, according to the researchers. This was reinforced by a larger study of 56 patients whose Alzheimer's had been definitively diagnosed at autopsy, they said.

The researchers had access to skin samples taken from the same patients and stored them in a tissue bank when they had revealed early Alzheimer's symptoms.

The ERK1:ERK2 ratios were then compared to 30 control patients who died from other brain diseases but who had also had skin placed in a tissue bank early in their disease.

The researchers have since obtained test results on a further 100 patients that have confirmed the distinctive ERK1:ERK2 activity ratio in Alzheimer's patients.

"So we are very hopeful indeed that this will translate into something clinically important," Alkon was quoted as saying.

Initial Alzheimer's symptoms, such as mild memory loss, are non-specific. The discovery of a simple diagnostic test, however, would allow doctors to intervene quickly with one of the new medications that are expected on the market in the next five years. In this way, progression of the disease might be halted before serious brain damage could occur, Alkon said.

Susanne Sorensen, head of research at the Alzheimer's Society in London, said the results looked very promising, as the way they were able to compare early and autopsy samples from the same patients was excellent -- although only a limited number of patients and controls were analyzed.

The test could be available within five years, the report quoted the researchers as saying. Enditem