The first new guidelines for diagnosing Alzheimer's disease in nearly 30 years establish earlier stages of the mind-robbing disease, paving the way for spotting and possibly treating these conditions much sooner than they are now.

The change reflects a modern view that Alzheimer's is a spectrum of mental decline, with damage that can start many years before symptoms appear. The new guidance describes three phases: early brain changes, mild cognitive impairment and full-blown Alzheimer's.

Yet the guidelines do not advise doctors to change how they evaluate and treat patients now. Despite the hoopla about new brain scans and blood and spinal fluid tests that claim to show early signs of Alzheimer's, they are not ready for prime time and should remain just tools for research, the guidelines say.

"It's too soon right now" to say these experimental biomarker tests will prove valid enough to be used in ordinary patient care, said Creighton Phelps, Alzheimer's program chief at the National Institute on Aging.

His institute and the Alzheimer's Association convened several expert panels to write the guidelines, the first since 1984. They are being published Tuesday in Alzheimer's & Dementia: The Journal of the Alzheimer's Association.

About 5.4 million Americans and more than 26 million people worldwide have Alzheimer's, the most common form of dementia.

"It's likely there are at least as many people with mild cognitive impairment as with Alzheimer's disease and maybe more," said William Thies, the Alzheimer's Association scientific director.

Even before this mild cognitive impairment shows up, brain changes such as a buildup of sticky plaque or protein tangles inside nerves can suggest trouble ahead.

Marilyn Albert, a Johns Hopkins University researcher who led the mild cognitive impairment panel, described this category as "people who have mild, progressive symptoms, changes in mental abilities, usually memory but not always memory" that stop short of full-blown dementia.

In doctors' offices around the country, "people are coming in with much milder symptoms," and many but not all will go on to develop Alzheimer's, she said.

How can doctors tell what's going on?

First, they try to determine how fast symptoms are progressing, and do tests to rule out an obvious cause such as a stroke or a new medication. If symptoms are gradual and progressive, doctors would likely diagnose mild cognitive impairment due to Alzheimer's. But they wouldn't know for sure without additional tests like the experimental biomarker and imaging scans rapidly being developed and researched, Albert said.

One company has asked for government approval of a new type of brain scan it claims shows early signs of Alzheimer's. Other companies are working on tests for substances in blood and spinal fluid. The guidelines say these are helpful for sorting people into clinical trials or monitoring the effects of experimental drugs, but not for routine use in clinics and doctor's offices.

Dr. Clifford Jack, a Mayo Clinic brain imaging specialist involved in the guidelines, explained why.

Unlike blood pressure tests that give fairly consistent readings regardless of what type of machine is used, the new biomarker tests are not yet standardized from one lab or location to the next, he said. There are no agreed-upon cutoffs or levels for how much of a substance indicates impairment or Alzheimer's. There's not even enough research to validate that a particular substance or biomarker truly predicts progression of disease, he said.

A bigger problem is what to do after impairment or dementia has been diagnosed. Current treatments do not alter the course of Alzheimer's, they just ease symptoms. Many doctors believe drugs are being given too late, after symptoms are severe, so researchers more recently have started testing some in people with mild cognitive impairment.

"If you're only going to try them in people with advanced dementia, the chance of them working is not going to be that great," said Dr. Guy McKhann of Johns Hopkins University, who headed one of the guideline panels.

Early diagnosis is a first step, and something the Alzheimer's Association has long advocated, Thies said.

"It allows people to anticipate what's going to happen in the future and plan their lives in ways to minimize the impact," he said. "People with the disease and their families cope better with their disease" if they know what to expect.

___

Online:

National Institute on Aging: http://www.nia.nih.gov

Alzheimer's Association: http://www.alz.org