Imagine you were able to have advance knowledge of Alzheimer's disease, perhaps by as much as several years, would you really want to know? The question may be loaded but it is no longer academic. The technology now exists to provide an early diagnosis of Alzheimer's.
Surgeons in Finland have used a test developed by William Klunk, Associate Professor of Psychiatry and Chester Mathis, Professor of Radiology and Pharmaceutical Sciences, both from the University of Pittsburgh. The test is used on living people. This last point is significant as, until now, the only reliable method to assess for brain plaques associated with Alzheimer's is after death or via living brain tissue samples, which requires invasive surgery.
The new test is a special kind of positron emission tomography (PET) scan. Known as the Pittsburgh Compound-B test (PiB), patients are first injected with a radioactive dye that attaches itself to proteins in the brain. The PET scan combined with PiB, currently lasts for 90 minutes, It is claimed to have a 90 percent rate of accuracy in its prediction of amyloid plaques, up to 10 years before the onset of dementia symptoms.
Before the PiB can be considered for use as a diagnostic tool for Alzheimer's disease, much larger and longer studies will be required to assess its overall value.
In the meantime we are left to speculate on the value we attach to a test for a disease that currently has no cure? From a patients perspective having advance knowledge of the disease could have a number of ramifications. Perhaps the most positive thing is the fact that it gives time to prepare. Wills can be drafted, legal aspects sorted out, transfer of responsibilities considered, and so on. However, the psychological implication is another thing altogether, and this is unchartered territory.
We already know that a diagnosis of Alzheimer's can have a profound emotional impact and may affect the person deeply in terms of their mental state, their work and their relationships. What are the implications if given advance notice of up to a decade? Will it help to soften the blow? Will it increase mental health problems? If the test is established as part of some regular screening, should people have the right not to know? This is a huge debate waiting to happen.
For the moment at least the greatest benefit of early diagnosis is to the medical profession. As new treatments become available it may be possible to prevent or slow the progression of dementia before the disease has established itself and damage cannot be reversed. PET scanning could also help doctors understand more about how the disease begins and progresses in the brain. The effectiveness of treatments could be monitored in a similar fashion.
The study was published online in the journal of the Archives of Neurology. It is expected to appear in the October print issue
Published On: August 18, 2008