A Skin Test for Alzheimer's

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Ann Persinger helps her mother Vivian, who suffers from Alzheimer's

Researchers at the Blanchette Rockefeller Neurosciences Institute report this week that they have solved one of the trickiest problems in Alzheimer's disease — finding a way to diagnose the condition while the patient is still alive. Now, the only way to definitively diagnose Alzheimer's is with a combination of clinical symptoms and autopsy. It's only after the patient's death that doctors can confirm the existence of the protein plaques that are the hallmark of Alzheimer's.

In a study published online by the Proceedings of the National Academy of Sciences, Dr. Daniel Alkon and his group describe a simple test for the disease using easily detected proteins found in skin cells. They claim that their test can provide enough information to detect the disease at its earliest stages, when treatments might be most effective. Even more encouraging, they report that the test is sensitive enough to distinguish Alzheimer's from other dementias, including Parkinson's disease.

Some experts are still cautious. Dr. Sam Gandy of the Alzheimer's Association finds the results intriguing, but emphasizes that they need to be replicated by other groups. "At this point, it's a very interesting piece of research data," he says. "It certainly bears efforts from independent labs to try and confirm it. Obviously, anything that helps with making a diagnosis early could be potentially beneficial — all the new drugs in clinical trials act at the very earliest stages of the disease. But I would not sell the farm to buy this until it's been replicated."

So while it's not quite ready for the doctor's office yet, it's still worth watching in coming years. This test, which could also lead the way to new drug treatments for Alzheimer's, incorporates some of the latest theories about how the disease gets started, and the best ways to treat it. Recent studies suggest that while it is a brain disorder, Alzheimer's earliest sign might be an imbalance in the body's immune system. This shows up as an inflammatory reaction that occurs not just in the brain cells, but throughout the body. The net effect of this imbalance is a build up of the toxic amyloid protein, which is poisonous to brain cells and triggers their progressive death. In fact, argues Alkon, the amyloid accumulates into sticky, fatty plaques because the inflammatory reaction shuts down production of the non-toxic, soluble form of amyloid that normally keeps the toxic form in check. Alkon's group picks up on enzymes that regulate the "good" amyloid; patients who develop the disease tend to have lower levels than those who don't end up with Alzheimer's.

So far, Alkon has used his test on 60 samples from patients with both the hereditary form of Alzheimer's, which hits patients earlier in life, and the more common, sporadic version that strikes in older age. He was also able to compare his test against autopsy confirmations, which were available for 20 of the samples. Among those, he says, the enzyme screen was 100% predictive.

Already the Rockefeller group has expanded its study to include over 100 more samples, and is close to testing a drug designed to boost the production of "good" amyloid. "We think we are getting at the core of the disease, at the very essence of it," says Alkon. Only time will tell if he is right.