Aug 16 2006
A simple skin test that would allow detection of Alzheimer's disease appears to be a realistic possibility in the future.
According to scientists at the Blanchette Rockefeller Neurosciences Institute (BRNI), substances in skin cells may provide doctors with a quick and accurate yes-or-no answer when they suspect a patient is showing early signs of the disease.
They say the test could be performed easily by a nurse or medical technician in a doctor's office or outpatient clinic.
The researchers at BRNI have apparently found a biomarker that can accurately distinguish between Alzheimer's disease and other forms of dementia during the first one to two years of the disease's progression.
The biomarker showed high rates of accuracy when it was tested with human skin cells from a tissue bank, as well as for samples obtained in a previous, unpublished study of patients with autopsy-confirmed diagnoses.
The biomarker also has the potential to be used with blood samples.
Dr. Daniel L. Alkon, M.D., scientific director of BRNI and coauthor of the study, along with with Tapan K. Khan, Ph.D., assistant professor, say that in the initial stages Alzheimer's disease is often difficult to distinguish from other dementias or mild cognitive impairment, but treatments for Alzheimer's are most effective before the devastating and widespread impairment of brain function that inevitably develops after four or more years.
Other scientists have found that Alzheimer's effects are found throughout the body and not just in the brain, but the BRNI team has located a biomarker for the disease by testing for signs of Alzheimer's-related inflammation in skin cells called fibroblasts, without the need for invasive tests previously required, such as a lumbar tap.
It seems that when Alzheimer's disease occurs it stimulates a change 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.
That particular imbalance is not seen in cells of people without dementia or those with other forms of dementia, such as Parkinson's disease, multiple infarct dementia and Huntington's chorea.
Drs. Khan and Alkon have created an Alzheimer's Index that may well help doctors' evaluations of dementia, which allows scientists to convert the test results for each patient to a single number.
Alkon says the test produced good results when run on 60 tissue samples: 30 from a tissue bank, and 30 from autopsy samples of people diagnosed with Alzheimer's disease.
An unpublished study of the test performed on 100 people showed equally good results, and the researchers say they are ready to expand this to thousands.
Experts say such expanded testing is essential, as the hypothesis behind the test is by no means an accepted formulation, nor have they proved it.
Though the presence of inflammation around the amyloid clumps that form in the brain of Alzheimer's patients is well known, whether there is inflammation elsewhere in the body has yet to be established.
Alkon says the results demonstrate that when the Alzheimer's Index agrees with the clinical diagnosis of the presence of Alzheimer's, there is a high probability of accurate diagnosis.
The research is published in the Proceedings of the National Academy of Sciences.
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