I guess I have a somewhat different take on the situation.
That the FDA had publicly recognized the difficulty of early stage AD diagnosis and the weakness of measuring tools has less to do with the FDA and much more to do with the state of the science and the difficulties of dealing with early stage CNS disease.
The brain is enclosed in a bone case. It is very delicate. The chemistry is complex.
Its not like liver disease where you can take enzyme measurements and see that the liver is in difficulty and then go in an take a biopsy to see what is going on.
The diseases we are discussing are not like a brain tumor that can been seen of PET scan or MRI. Early stage CNS diseases are occurring at the molecular level on small numbers of neurons. The brain has amazing compensation capabilities that disguise the effects of early degradation of function.
What we are seeing is that brain science is still in the early stages with all of the limitations that go with that state of affairs.
The brain is amazingly complex on the chemical, electrical, molecular levels. There are complex systems of rhythms, hormones, emotions, all interacting, most of which have feedback loops into other systems/parts of the brain.
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