New guidelines for Alzheimer’s could lead to earlier diagnosis

NEW YORK — For the first time in 25 years, medical specialists are proposing a major change in the criteria for Alzheimer’s disease, part of a new movement to diagnose and, eventually, treat the disease earlier.The new diagnostic guidelines, presented yesterday at an international Alzheimer’s meeting in Hawaii, would mean that new technology such as brain scans would be used to detect the disease before there are evident memory problems or other symptoms.

If the guidelines are adopted in the fall, as expected, some specialists predict a two- to threefold increase in the number of people diagnosed with Alzheimer’s disease. Many more people would be told they probably are on their way to getting it.

The changes could also help drug companies that are developing new drugs to try to attack the disease earlier. So far, no drugs alter the course of the disease.

Development of the guidelines, by panels convened by the National Institute on Aging and the Alzheimer’s Association, began a year ago because, with a new understanding of the disease and new ways of detection, it was becoming clear that the old method of diagnosing Alzheimer’s was sorely outdated.

The current criteria for diagnosing Alzheimer’s require steadily progressing dementia — memory loss and an inability to carry out day-to-day activities — along with a pathologist’s report of plaque and another abnormality, known as tangles, in the brain after death.

But researchers now believe the disease is present a decade or more before dementia.

“Our thinking has changed dramatically,’’ said Dr. Paul Aisen, an Alzheimer’s researcher at the University of California at San Diego, who is helping formulate the new guidelines. “We now view dementia as a late stage in the process.’’

The new guidelines include criteria for three stages: preclinical disease, mild cognitive impairment due to Alzheimer’s disease, and, lastly, Alzheimer’s dementia. The guidelines should make diagnosing the final stage of the disease in people who have dementia more definitive. But the guidelines also say that the earlier a diagnosis is made the less certain it is. So the new effort to diagnose the disease earlier could, at least initially, lead to more mistaken diagnoses.

Under the new guidelines, diagnoses will aim to identify the disease as it is developing by using results from so-called biomarkers — tests like brain scans, MRI scans, and spinal taps that reveal telltale brain changes.

The biomarkers were developed and tested only recently, and none has been formally approved for Alzheimer’s diagnosis. One of the newest, a PET scan, shows plaque in the brain. The others provide strong indications that Alzheimer’s is present, even when patients do not yet have dementia or much memory loss.

Aisen says he foresees a day when people in their 50s routinely have biomarker tests for Alzheimer’s and, if the tests indicate the disease is brewing, take drugs to halt it. That is not expected soon, he says, but “it’s where we are heading.’’

“This is a major advance,’’ said Dr. John Morris, an Alzheimer’s researcher at Washington University in St. Louis who helped write the guidelines. “We used to say we did not know for certain it was Alzheimer’s until the brain is examined on autopsy.’’

By Gina Kolata
New York Times / July 14, 2010