Rick,

I agree with you that there will probably be some things that research overlooks- I'm going with the 'major' markers targeted by researchers. Right now in clinical trial, there is a biomarker study that targets only 3 in our poll (anosmia, REM Disorder, and Hypotension). I have read that gastric changes and anxiety/depression were also prevalent but I don't know they're being tested. I was surprised; however, to learn that hypotension was being marked.

As for use in diagnosis, I'm just going by what is posted at MJFF, but maybe I'm extrapolating where not warranted. According to the report:

Disease state biomarker: a 'diagnostic' marker that a given individual has PD (particularly useful for distinguishing PD from other PD-like diseases or for identifying individuals in the earliest stages of the disease).

Clinical measures (e.g., tests of motor ability, presence of disease-associated symptoms such as olfactory deficits, sleep disorders, constipation or early speech problems) can be good markers, but it may be necessary to combine more than one for reliable results. These measures are also not necessarily Parkinson's-specific.

Right now, there is actually a scratch 'n sniff card used in research now; the University of Penn Smell Identification Test. Even more interesting is that there is a small percentage of us (10% or so) who do not lose sense of smell and there may be a differential here between having Parkin Disease (hereditary) and Idiopathic PD. Not to say that this test is the be all and end all, but I fall into that minority range, and would really like to know more of genetics involved here for sake of my young son.