In July, panels sponsored jointly by the National Institute of Aging and the Alzheimer's Association presented controversial proposed guidelines for diagnosing Alzheimer's at three different stages of its progression: 1) preclinical, 2) mild cognitive impairment, and 3) classic dementia.
The preclinical panel stated that laboratory testing (i.e. PET or MRI scans, spinal taps, or blood tests) before the appearance of symptoms was meant to be purely for research. But, the other two panels seemed to suggest that laboratory testing was ready, or soon would be ready, to be used in routine clinical practice in diagnosing mild cognitive impairment or dementia. Faced with widespread skepticism, the panels held a conference call yesterday to clarify their position. As reported by Gina Kolata in The New York Times, there is reassuring new information. The panels recognize that laboratory testing is still only a research tool and will not be recommending that it be included as part of current clinical diagnosis. This makes great sense. All the available tests are at an early stage of development and are not nearly ready for routine use.
Rapid strides are being made in the study of Alzheimer's disease, with powerful new methods leading us closer to understanding its causes and mechanisms. But let's not jump the gun and mislead ourselves or the public into the false beliefs that a diagnostic breakthrough has already been made and that a treatment breakthrough is possible in the near future.
It is pretty easy to show that a promising laboratory procedure yields different group mean values when comparing Alzheimer's to a control group. It is very difficult to prove that it has sufficient reliability, accuracy, clinical utility, and cost effectiveness to become a useful diagnostic test worthy of use in routine clinical practice. It will require years of testing in very varied populations before we will learn if any of the currently available candidates is indeed the long awaited diagnostic test for Alzheimer's.
It is understandable that Alzheimer's experts have a strong desire to become preventively proactive. Can amyloid be the early marker of Alzheimer's, in analogy to cholesterol and heart disease? Can early identification and early intervention prevent the ravages of the disease? The problem is that you simply cannot skip the middle steps. Do the research first, then publish the guidelines.
And we should also be cautious in our expectations for a treatment breakthrough. It is possible that learning more about the mechanisms of Alzheimer's may eventually lead to the development of a rational cure or preventive, but it is equally possible that it will not. The general experience in medicine over the past three decades is that an exponential explosion in knowledge about a disease does not often lead to any immediate miracle cure. Moreover, the lack of success to date in developing medications for Alzheimer's does not inspire confidence. The available drugs -- although they have been highly profitable to the drug companies -- have little, if any, efficacy for patients. Attempts to develop a new generation of effective drugs have so far failed despite considerable investment. There does not appear to be any low-hanging fruit.
We should have and encourage reasonable hope regarding advances in Alzheimer's, but should avoid hype and hoopla. Progress will be steady, but probably much slower than suggested by the recent excitement.
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