Potential for New Blood Test for Alzheimer’s

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With the Alzheimer’s Association preparing to release new guidelines for diagnosing the degenerative brain disease ever earlier in a patient’s lifetime, the race is on to find new and simpler ways of testing for the disorder. And what could be easier than a blood test?

Researchers led by Sid O’Bryant at the Texas Alzheimer’s Research Consortium identified a group of more than two dozen proteins circulating in the blood that may be elevated in those with Alzheimer’s, compared to those who are mentally healthy. The suite of blood markers was 80% accurate in identifying patients who had the disease, and 91% accurate in excluding healthy individuals.

“I look at this, and say this is great research. It’s really important. Early identification [of patients] is something we all think is important, since the sooner people know [they are at risk], the sooner they can take a variety of actions,” says Dr. William Thies, chief medical and science officer for the Alzheimer’s Association.

But Thies warns that as exciting as such tests are, they represent only the first steps on a long road toward an effective and reliable test for the doctor’s office. Researchers have recently been flooding journals with reports of different diagnostic tests, from blood-based screens to imaging techniques and even studies of fluid from the spinal column. All are aimed at teasing out the strongest and most reliable harbingers of the proteins that build up in the brains of Alzheimer’s patients.

So far, blood-based tests have been unsuccessful in picking up changes in the brains of affected individuals, but O’Bryant is confident that the proteins his group has identified may be part of a multipronged approach to finding the elusive diagnostic key to the disease.

Previous work by Stanford researchers in 2007 revealed a panel of 18 proteins in the plasma portion of blood that seemed to be linked to a higher risk of the disease. O’Bryant’s proteins are found in the serum of blood, a slightly more accessible component of a basic blood test, and for the most part are different from the earlier suite of proteins. Most of the newly isolated proteins, he says, are related to inflammatory processes that may be a byproduct of the accumulation of plaques in the brain as Alzheimer’s disease progresses.

The next step will be to test his panel in a larger group of patients to confirm that it accurately separates people who have the degenerative disease from those who do not. Then, says O’Bryant, he will also test whether the proteins can screen individuals with mild cognitive impairment, the first stages of Alzheimer’s, to predict which patients are more likely to develop the advanced form of the disease or progress faster toward dementia.

But even if these tests validate the current findings, O’Bryant acknowledges that such a screen won’t likely be the only tool that doctors should use in identifying those at high risk. Even in his study, combining the protein screen with other known risk factors for Alzheimer’s, including age and genetic data, predicted the disease better than the proteins alone.

The findings only hint at the power that such biological markers can have in diagnosing a disease as complex and as devastating as Alzheimer’s. “This is a really important area,” says Thies. “There is a growing consensus in the field that in order to get effective interventions, we are going to have to have medications given very early in the course of the disease.” And the sooner the condition can be diagnosed, the earlier these treatments can begin.

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