It may be possible to develop a quick, painless skin test for Alzheimer's disease, scientists say.

US researchers say they have discovered enzymes that react abnormally only in the skin of Alzheimer's patients. 

Currently, the disease can only be diagnosed using psychiatric assessments or during a post-mortem examination. 

The study, by Maryland's Blanchette Rockefeller Neurosciences Institute, features in Proceedings of the National Academy of Sciences. 

The researchers said their test would be able to distinguish Alzheimer's from other brain-damaging diseases, such as Parkinson's. 

When it begins, Alzheimer's is often difficult to distinguish from other conditions - or even from mild cognitive impairment. 

But early diagnosis of the condition is key because drugs to slow its progress have the most effect when administered when the disease is still in its earliest stages. 

The researchers found Alzheimer's stimulated a change in enzymes called MAP Kinase Erk 1 and 2. 

They carried out tests on tissue samples taken from people who had died from various known causes, including Alzheimer's. 

The Erk 1/2 response to the inflammatory chemical, bradykinin, was different in samples from Alzheimer's patients to that seen in tissues taken from other people. 

'Profound implications' 

Dr Susanne Sorensen, head of research for the Alzheimer's Society, said current tests for the condition were difficult to justify as they were invasive and only 85% effective. 

"If the skin test can be successfully developed it will revolutionise early diagnosis of dementia. 

"Doctors will be able to do tests much earlier and this will go hand in hand with future treatments and vaccines that are helping people to stabilise their dementia before problematic and distressing symptoms emerge. 

"These results look very promising but further research is now needed to see whether the skin test can be successfully developed to screen people with early memory problems for Alzheimer's disease." 

Rebecca Wood, chief executive of the Alzheimer's Research Trust, said the research bolstered the evidence that the disease involved changes not just to the brain but to a variety of other organs too. 

She said it was particularly interesting that the biomarker was most pronounced in samples from people experiencing the earliest stages of the disease, as opposed to those whose condition was more advanced. 

This high level of initial specificity would be particularly helpful in any early diagnostic test. 

"Identifying individuals before they display obvious clinical symptoms is a very important area of research which could have profound consequences for patients and their families. 

"We need to be able to identify people before they develop symptoms so that any future treatments could be started as quickly as possible - before the brain has been too injured." 
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