MONDAY, Aug. 14, 2006 (HealthDay News) -- A simple skin test that would allow detection of Alzheimer's disease in its earliest stages is working its way to reality.
The work "is based on the hypothesis that Alzheimer's disease doesn't just affect the brain but affects the body systemically," said Dr. Daniel L. Alkon, a lead author of a report on the test published online this week in Proceedings of the National Academy of Sciences.
The test zeroes in on two forms of an enzyme involved in the degradation of amyloid, the protein that accumulates in the brain of someone with Alzheimer's, said Alkon, scientific director of the Blanchette Rockefeller Neurosciences Institute at the West Virginia University Health Sciences Center.
The presence of Alzheimer's disease is indicated by a steep imbalance in the ratio of the two forms of the enzyme, MAP kinase Erk, in skin cells that are exposed to bradykinin, an inflammation-related molecule, Alkon said. That imbalance is not seen in cells of people without dementia or those with other forms of dementia, he said.
The test produced good results when run on 60 tissue samples: 30 from a tissue bank, 30 from autopsy samples of people diagnosed with Alzheimer's disease, Alkon said.
"We have seen a correlation with the duration of the disease," he said. "The earlier it is done in the course of the disease, the larger is the abnormality."
An as-yet unpublished study of the test done on 100 people showed equally good results, Alkon said.
"We are ready to expand this to thousands," he added.
Such expanded testing is essential, said Dr. Samuel Gandy, director of Thomas Jefferson University's Farber Institute for Neurosciences and chief of the Alzheimer's Association medical and scientific advisory council.
The hypothesis behind the test "is, by no means, an accepted formulation, nor have they proved it," he said.
The presence of inflammation around the amyloid clumps that form in the brain of Alzheimer's patients is well known, Gandy said. "Whether there is inflammation elsewhere in the body hasn't been established. The idea that this might be a systemic process hasn't been thoroughly investigated," he added.
Gandy said the theory is "unconventional, but it certainly is something that can be investigated by others."
"Technically, it looks perfectly sound," Gandy said of the published paper. "But certainly nothing in science is accepted until it is replicated. The real test of the pudding will be if others do the same experiment and get the same results. It would have to be robustly reproducible before we change the way we think about Alzheimer's."
Having a test for early detection of Alzheimer's disease would be extremely valuable, both Alkon and Gandy said. "All the newest medications in clinical trials are aimed at the earliest stage of the disease," Gandy said.
"Drugs now are being tested on the basis of clinical diagnosis," Alkon said. "There is a major need for an early biomarker."
A major source of information about Alzheimer's disease is the Alzheimer's Association.