CHICAGO - RESEARCHERS have developed a simple blood test that may be able to predict whether mild lapses of memory could be an early sign of Alzheimer's disease.

In a study published on Sunday in the journal Nature Medicine, an international team of researchers describe 18 cell-signalling, or communication, proteins found in blood that predicted with 90 per cent accuracy whether a person would develop Alzheimer's disease.

They said tests to detect changes in these proteins could be used to predict the disease two to six years ahead of its onset and may be useful in the search for treatments.

'This is very exciting,' said Dr Tony Wyss-Coray, a researcher at Stanford University and head of geriatric research at the Veterans Affairs Palo Alto Health Care System in California.

'We show there are very interesting changes going on with patients with Alzheimer's disease. These changes occur early on in the disease process,' Dr Wyss-Coray said in a telephone interview.

Alzheimer's disease is a progressive, degenerative disease that robs people of memory, reasoning and the ability to communicate. According to the World Health Organisation, about 18 million people worldwide have the disease.

Currently, doctors diagnose Alzheimer's disease by excluding other potential causes of memory loss, such as stroke, tumours and heavy drinking. They can also administer simple paper-and-pencil tests.

Brain scans are also used, but the only definitive diagnosis is an autopsy.

Searching for a 'fingerprint'
Researchers in the study wanted to see if they could spot specific patterns in the blood of people with Alzheimer's disease that might offer a profile or fingerprint for the disease.

They collected 259 blood samples from people with early signs of Alzheimer's to late-stage disease as well as people with no symptoms at all.

They were able to measure levels of 120 known proteins found in blood plasma that work as chemical messengers between blood cells, brain cells and cells in the immune system.

An analysis of these uncovered 18 proteins that are expressed in different concentrations in people with Alzheimer's disease.

Researchers found two important functions were suppressed in the Alzheimer's patients - systems for making new blood cells and also systems used in immune function, said Wyss-Coray, who is also co-founder of privately held Satoris Inc, a development-stage company that hopes to commercialize the test.

In blood samples taken from 92 people who ranged from no symptoms to full dementia, the analysis matched the actual diagnosis in 90 per cent of the cases.

To see if the test could predict who would develop Alzheimer's disease, they tested stored blood samples from 47 people with mild memory impairments who had been followed for two to six years.

The test was accurate 91 percent of the time at flagging which individuals went on to develop the disease.

The study was part of a collaboration between Satoris and several dementia centres in the United States and Europe.

Patrick Lynn, president and chief executive officer of Satoris, said he hopes to develop a test that can be used in research centres by 2008. But first the study must be replicated by other labs and in larger studies. -- REUTERS