CHICAGO (Reuters) - Proteins in spinal fluid accurately detect early-stage Alzheimer's disease in patients and could pave the way for better drug research, Swedish researchers said on Tuesday.

Several teams have been working on better ways to detect early-stage Alzheimer's disease in hopes of developing drugs that can fight it before it causes too much damage.

"We confirmed in a large multi-centre study that these (cerebrospinal fluid) biomarkers may identify early-stage Alzheimer's disease, which has previously been suggested in earlier smaller studies," Dr. Niklas Mattsson of the University of Gothenburg in Sweden, whose study appears in the Journal of the American Medical Association, wrote in an e-mail.

Mattsson said the current study in patients with mild cognitive impairment or MCI, a precursor to Alzheimer's disease, strengthens the argument that proteins in spinal fluid can accurately show who has early-stage disease.

This may also be useful in structuring smaller clinical trials to test whether a drug is working. Current diagnostic measures, such as neurological and memory tests, are less accurate, forcing drug companies to run large, expensive clinical trials to show their drugs work.

"The drug industry certainly fears failure of these large scale studies and biomarkers may save millions of dollars in addition to allowing a more rapid development of efficient drugs," Mattsson said.

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

The team studied three proteins — two types of tau, which forms toxic tangles in the brain and a form of amyloid, which forms sticky brain plaques in people with Alzheimer's disease.

Although they affect the brain, bits of the proteins were also found in the cerebrospinal fluid, which bathes both the brain and the spinal cord.

"These biomarkers ... reflect core elements of the disease process in the brain in Alzheimer's disease," Mattsson said.

His team studied 750 people with mild cognitive impairment, 529 with Alzheimer's disease and 304 healthy people in 12 centres in Europe and the United States. People with cognitive impairment were followed for two years, or until their symptoms worsened.

The researchers found the three biomarkers accurately identified 62 percent of those who would develop Alzheimer's disease, and were 88 percent accurate at ruling it out.

The team said the findings were a bit less accurate than results seen in smaller studies, and suggest standardized testing techniques might improve results.

Drs. Ronald Petersen of the Mayo Clinic in Rochester, Minnesota, and John Trojanowski of the University of Pennsylvania School of Medicine in Philadelphia, wrote in a commentary that the results were sufficient for screening patients, but not as a diagnostic test.

"Alzheimer disease has no treatment to prevent or alter the course of the disease, so making the diagnosis with good accuracy may aid in planning but also could be devastating news for some patients and families," they wrote.