Study shows spinal-fluid test can be 100 percent accurate predicting Alzheimer's

By Gina Kolata
The New York Times
Posted: 08/10/2010 01:00:00 AM MDT

Researchers report that a spinal-fluid test can be 100 percent accurate in identifying patients with significant memory loss who are on their way to developing Alzheimer's disease.

Although there has been increasing evidence of the value of this and other tests in finding signs of Alzheimer's, the study, which will appear today in the Archives of Neurology, shows how accurate they can be. The new result is one of a number of remarkable recent findings about Alzheimer's.

Alzheimer's, medical experts now agree, starts a decade or more before people have symptoms. And by the time there are symptoms, it may be too late to save the brain. So the hope is to find good ways to identify people who are getting the disease and use those people as subjects in studies to see how long it takes for symptoms to occur and in studies of drugs that may slow or stop the disease.

Researchers are finding simple and accurate ways to detect Alzheimer's long before there are definite symptoms. In addition to spinal-fluid tests, they have new PET scans of the brain that show the telltale amyloid plaques that are a unique feature of the disease.

And they are testing hundreds of new drugs that, they hope, might change the course of the relentless brain-cell death that robs people of their memories and abilities to think and reason.

"This is what everyone is looking for, the bull's-eye of perfect predictive accuracy," Dr. Steven DeKosky, dean of the University of Virginia medical school, who is not connected to the new research, said about the spinal-tap study.

The study included more than 300 patients in their 70s, 114 with normal memory, 200 with memory problems and 102 with Alzheimer's disease. Their spinal fluid was analyzed for amyloid beta, a protein fragment that forms plaques in the brain, and for tau, a protein that accumulates in dead and dying nerve cells in the brain. To avoid bias, the researchers analyzing the data did not know anything about the clinical status of the subjects. Also, the subjects were not told what the tests showed.

Nearly every person with Alzheimer's had the characteristic spinal-fluid protein levels. Nearly three quarters of people with mild cognitive impairment, a memory impediment that can precede Alzhei mer's, had Alzhei mer's-like spinal-fluid proteins. And every one of those patients with the proteins developed Alzheimer's within five years.