Monday, July 28, 2008

Early-diagnosis blood tests for Alzheimer's disease in development

[Source: Shari Roan, Los Angeles Times Staff Writer] - People with Alzheimer's face an awkward juncture in the near future. They'll be able to learn early on whether they have Alzheimer's disease -- even if they can't do much about it.

With therapies to halt or slow the progression of Alzheimer's disease seeming ever more elusive, several blood tests currently in development could determine who has the disease even before symptoms develop or become severe. Researchers say they believe people would use such a test, if only to prepare for a future with the limitations wrought by dementia."It would be a boon to the field," says Dr. Ronald C. Petersen, a neurologist at the Mayo Clinic in Rochester, Minn. "Many, many people are at risk due to family history, age, genetic characteristics. But we don't have a good prediction formula for who will actually get the disease."

Alzheimer's disease is extremely difficult to diagnose in its early stages because the symptoms, such as memory problems, can also be attributed to normal aging or a number of other illnesses. Even the appearance of plaque in the brain is not considered a telltale sign of the disease because some older people have plaque but do not suffer from dementia. Doctors and patients need a test that is convenient, accurate, reliable and inexpensive, says Dr. Harold Varmus, the former director of the National Institutes of Health and a member of the Alzheimer’s Study Group(ASG), an independent working group mandated by Congress to develop a national strategic plan for Alzheimer's disease.

"It's clear that finding this disease at the earliest possible stage provides the best possible window for therapeutics," Varmus says. "If you can make an early diagnosis, you can think about trying to arrest the disease, which is better than trying to reverse it."

Targeted at research

A Redwood City, Calif., company, Satoris Inc., has announced plans to release a blood test for use in research later this year. A study published in the journal Nature Medicine in November examined blood samples from 259 people who had early- to late-stage Alzheimer's disease or did not have the disease. It found 18 proteins in the blood of Alzheimer's patients with concentrations different from normal individuals. The protein panel allowed for nearly 90% accuracy in diagnosing and characterizing the disease even among people with only a mild version of the disease called mild cognitive impairment.

The as-yet-unnamed test would be used initially with other diagnostic tests, such as brain scans, to provide a highly reliable result, says Cris McReynolds, president of Satoris. "It will be an important piece of information used with other information to make an accurate diagnosis."

McReynolds says he hopes a test for the general public will become available one or two years after researchers begin their work with it.

Another test, called NuroPro, is under development by Power3 Medical Products in the Woodlands, Texas. It measures 59 protein markers in the blood that distinguish people with Alzheimer's disease from those with Parkinson's disease as well as those without either disease. Data from a study by Sun Health Research Institute in Sun City, Ariz., are expected at the end of August, says Steven Rash, chief executive of Power3. He says the company hopes to launch a test for the public late this year.

It's too soon to tell if these tests are accurate enough to be diagnostic tests or if they may just suggest a higher risk for the disease, Petersen says.

Diagnostic tests that appear reliable in academic research settings may not be as impressive in the general population where "you take all comers," says Dr. P. Murali Doraiswamy, chief of biological psychiatry at Duke University and co-author of the new book "The Alzheimer's Action Plan."

"We should be cautious in applying this technology," he says. "I think people have a right to know, but at the same time people should be counseled fully and not be led into getting these tests without knowing the risks and benefits."

Test may lead to drug

The real value for a diagnostic blood test, at least initially, may be in research. Scientists are also optimistic that an early-diagnosis blood test will spark better drug trials and, ultimately, a blockbuster medication.

Many researchers believe that previous Alzheimer's drug trials have been hindered by inaccurate methods to identify subjects -- people who have the disease rather than some other type of dementia -- and by inferior tools to gauge a drug's effectiveness, such as through cognitive testing or asking people or their family members if the symptoms have improved.

Says McReynolds: "They have been operating in the dark."

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