Blood Test May Predict Alzheimer's Disease

Oct. 14, 2007 — -- Alzheimer's experts are optimistic that a new type of blood test could one day allow doctors to accurately predict one's risk of developing the degenerative disease.

While prior research has suggested that imaging techniques and tests on spinal fluid could also be used to predict the risk of Alzheimer's, a study published in the current issue of the journal Nature Medicine suggests that this goal could be accomplished with a simple blood draw.

Such a test, if proven effective, would be less costly than imaging techniques and less invasive than a spinal tap.

Lead study author Dr. Tony Wyss-Coray, associate professor of neurology and neurological sciences at Stanford University in Palo Alto, Calif., said the test would not only identify the presence of Alzheimer's, but would also provide clues as to whom is on a path to develop the condition.

Researchers compared a total of 259 blood plasma samples -- some from patients with Alzheimer's, and the rest from patients without the disease.

What they found were 18 signaling proteins in the blood plasma that were 90 percent accurate in classifying those who may develop Alzheimer's disease two to six years later.

Thus, by taking a sample of blood and examining the proteins in the plasma, he explained, a doctor "may get an idea if a disease process is going on. ... We are almost listening to the language of cells."

Although Wyss-Coray said that the test will not be available for "a couple of years," he is already excited about its implications.

"It might be possible to get a sample of blood to determine if they [the patients] are on a path or have it [Alzheimer's]," he said.

Others in the field are equally optimistic. Dr. Paul Kettl, professor of psychiatry at Penn State College of Medicine, said these results are "more significant, and success rates are better" compared to other potential tests.

Blood Better Than Imaging?

The study, however, is not the first to suggest the possibility of an effective screening measure for Alzheimer's. Indeed, many whose lives are affected by the disease may be reluctant to hope that this research will yield results, since many previous studies have as yet failed to manifest life-altering advances.

What this new test would bring to the table, Wyss-Coray said, is the prospect of "easy and affordable tests."

Dr. Yuval Zabar, a neurologist at the Lahey Clinic in Burlington, Mass., also appreciates its relative simplicity.

"The most significant aspect of this study is the potential for prediction of progressive cognitive decline using a simple blood test," he said.

Why Does It Matter?

Since there is as yet no "cure" for Alzheimer's, many may wonder why anyone would want to be tested. However, Dr. Ron Petersen, director of the Alzheimer's disease research center at the Mayo Clinic in Rochester, Minn., said the earlier someone knows their likelihood of developing the debilitating disease, the better.

"It becomes crucial to have an early marker of disease risk such that interventions can be initiated as early as possible," he noted.

Thus, having a relatively simple tool to detect the disease early could pay big dividends in terms of health and treatment.

And an easier means of early detection may also safeguard the health of those in the early stages of the disease. Wyss-Coray notes that Alzheimer's patients often "forget to take medications for other conditions such as diabetes, heart disease, and hypertension," complications that may be avoided if caregivers are alerted early to the possibility of the condition.

Other physicians agree.

"This [early identification] should be advocated," said Dr. Rachelle Smith Doody, director of the Alzheimer's disease and memory disorders center at the Baylor College of Medicine in Houston.

"It benefits patients to be given information on their condition and to go on therapy," she continued. "It prevents the patient from receiving contraindicated or unneeded therapies, and it helps the patient, family and clinician develop a management plan."

What's the Catch?

Although the benefits are plentiful, some experts cite caveats.

"The markers mentioned are not routine, and the assays are not universally available," Zabar said, noting his concern that the tests will be marketed at very high cost through a private laboratory.

Zabar adds that he also doubts whether insurance is likely to pay for it, a concern emanating from "what happened to spinal fluid biomarker tests in the past."

Wyss-Coray disagrees.

"The markers are not novel, and assays exist for them," he said.

He adds that the pharmaceutical company Satoris is already developing a kit that combines all of them in a simple assay and the "cost would be significantly lower than imaging."

Like Wyss-Coray, Petersen concurs that "this would be an inexpensive test."

Petersen, who agrees the test would likely be inexpensive, nonetheless points out a different drawback: The study will need to be replicated in larger samples to confirm that these tests are reliable.

Dr. Mark Tuszynski, director for the center for neural repair at the University of California, San Diego, agrees.

"Limitations are that the data are from a small sample set and will very much need to be replicated on a larger patient set," he said.

"But if this holds up on subsequent, larger analysis," Tuszynski added, "it could have significant public health implications on many, many levels."

Despite current limitations, Alzheimer's experts agree that this test could have significant positive implications in the future.

After all, Wyss-Coray noted, "there are a quarter of a million Alzheimer's patients per year who are not diagnosed."