New tests assessing brain changes and body chemistry are showing promise at diagnosing Alzheimer's disease in its earliest stages, aiding the search for new drugs, Irish researchers said on Tuesday.

A team from Trinity College in Dublin found scans measuring brain volume and a combination of memory tests accurately identified nearly 95 percent of people who had progressed from mild cognitive impairment to early Alzheimer's disease.

The findings, presented at an Alzheimer's Association meeting in Vienna, Austria, are some of the first from a five-year, $60 million study aimed at identifying brain changes that signal the advance of Alzheimer's disease.

"The idea is if there could be biological markers identified that tracked what was going on in the brain, this would give you a better idea of whether a drug was having a biological effect," Neil Buckholtz, who heads the U.S. National Institute on Aging's Alzheimer's Disease Neuroimaging Initiative, or ADNI, said in a telephone interview.

The study, which is funded with U.S. government and industry funds, involves more than 800 people looking at brain structure and biological changes such as in spinal fluids that could signal disease progression.

Despite decades of research, doctors still have few effective treatments for Alzheimer's disease, a mind-robbing form of dementia that affects more than 26 million people globally and is expected to reach 100 million by 2050.

Only an autopsy revealing the disease's hallmark plaques and tangles in the brain can offer a definitive Alzheimer's diagnosis. Short of that, doctors use neurological and memory tests. Because they are subjective, drug companies must run large, costly trials to show their drugs work.

Biomarkers may lead to cheaper trials, Buckholtz said.

In the Irish study, Michael Ewers of Trinity College and colleagues studied 345 participants in the ADNI study with mild cognitive impairment, a precursor to Alzheimer's.

They looked at an array of tests and found three memory tests plus MRI measurements of brain volume in the left hippocampus -- a region closely linked to memory -- were most predictive of disease progression.

Buckholtz expects many more studies to come from the ADNI study. "The idea is we are trying to define the best biomarkers or combination of biomarkers that will allow us to assess progress," he said.

In another study presented at the meeting, a team at Duke University in North Carolina led by Dr. Allen Roses found that a gene called TOMM40 raises Alzheimer's risk.

The gene predicted the age of Alzheimer's development within a five- to seven-year window in people over 60. It is closely linked to another Alzheimer's gene called ApoE4.