New test diagnoses Alzheimer's disease

A test that can identify with spot-on accuracy which patients with early memory loss will develop Alzheimer's disease, left experts divided Tuesday on whether widespread screenings will result any time soon.

An international team of scientists, reporting in the Archives of Neurology Tuesday, pinpointed three key proteins in spinal fluid that provide early evidence of the mind-robbing disorder. The team found the telltale markers not only in the cognitively impaired but also in more than a third of test subjects who were cognitively healthy.

Currently, a definitive diagnosis of Alzheimer's is made during autopsy, though recent advances in imaging have helped doctors more accurately diagnose and distinguish it from other forms of dementia.

The latest test was 100 percent accurate in identifying the proteins - and for those with mild cognitive impairment was accurate as a predictor of Alzheimer's within five years.

But because the test is cumbersome and still only available as a research tool, it's considered an unlikely method of early detection in the immediate future.

Experts noted that other forms of predictive screening remain under study and might yet emerge as more suitable methods for a disease that has so far defied both early detection and treatment.

"This is a research test and it will not come to anyone's local physician in the near future," said Dr. Bill Thies, chief medical and scientific officer at the Alzheimer's Association. "But this lets us know which people have the early stages of the disease and whether we can track them from when they have very few symptoms to when they have more."

Alzheimer's is usually diagnosed in the moderate to late stages when the brain is seriously damaged. The hope is that by identifying the disease earlier, treatment can be initiated sooner to slow its progression. Experts acknowledged the latest findings would help researchers better understand how the disease progresses over time. But the test also raises questions.

"They found a third of people who are cognitively normal had this kind of [protein] signature and that raises the question whether Alzheimer's pathology is evident many years in advance," said Dr. Marc L. Gordon, a neurologist at Litwin-Zucker Research Center for the Study ofAlzheimer's Disease and Memory Disorders in Manhasset.

Dr. Neil Buckholtz, chief of the Dementias of Aging Branch at theNational Institute on Aging said the study dealt only with people involved in ongoing clinical research: "We still don't quite understand what this means in the larger community."

Scientists examined spinal fluid removed through lumbar puncture in 400 patients studied at the University of Ghent in Belgium and theUniversity of Pennsylvania. A series of three key proteins were found in 90 percent of people with Alzheimer's; 72 percent of people with mild cognitive impairment and 36 percent of people who were free of any brain condition.

Buckholtz noted another concern: There is not yet a standardized way to measure two of the three proteins. Researchers developed their own protocol to measure these proteins in the study but ways of measuring them vary in the larger medical community.

Despite the study's drawbacks, Buckholtz described it as an important finding because it definitively highlighted the role of the three proteins.

Pioneering Alzheimer's researcher Dr. Peter Davies, of the Feinstein Institute for Medical Research in Manhasset, said doctors need more than one test to make predictions - or a diagnosis - of a disease as complex as Alzheimer's. "This is not a test that we would rely on," he said.

The disease afflicts more than 5 million Americans, and is expected to become an even more major public health concern as the generation of baby boomers ages.