Debi
I've been in enough clinical trials to know that both measurements are quite ambiguous, especially the Hoehn & Yahr. OK - we have a teachable moment here!
Hoehn & Yahr is a simple scale that rates theh stages of one's progression of Parkinson's. For the trial I was in, one had to be 3.5 (but that's fudging s bit). The scale is 1 to 5 (5 being the worst). In laymen terminology, 0 is the absence of any symptoms; 1 is tremor or only one side affected (a foot that drags, a tremor in one hand, etc.) At stage 2, both sides are affected, and 3 just adds balance problems. Many of us fall under 3 on this scale. If you are a 4 - you need a lot of assistance, and probably have to be in a long-term care or assisted living setting. Then the infamous 5 rates one as confined too a wheelchair or bedfast. I have been between 3 and 4 for a long time. The H&Y is just a rating instrument using observable symptoms only.

Here are the details:
http://www.allaboutparkinsons.com/ho...ahr-scale.html

Th UPDRS (United Parkinson's Disease Rating Scale) is MUCH longer and more detailed - it also includes questions about your quality of life, activities of daily living, Mood etc.
http://www.neuropsicol.org/Protocol/Updrs.pdf

Although not nearly as unreliable as the H&Y, the UPDRS has been under fire for needing change due to many areas being unreliable because of the subjective nature of the questions. And although the UPDRS has some non-motor symptom questions, it doesn't dig deep enough into the non-motor stuff.

Recently, I attended the Office of Biotechnology Activities and NIH Sham neurosurgery conference, and this was a bone of contention with me. In my opinion, Parkinson's is as much a mood disorder as it is a movement disorder. I made this very statement at this conference adding "If we don't start assessing both mental/mood status parallel wih motor skills, we will never find a cure for Parkinson's." I also mentioned that although there had been some changes to the UPDRS , there was still too much leverage with interrater bias. No one argued with me.

Here is an abstract on a validation study of the mental/mod part of the UPDRS:
http://www3.interscience.wiley.com/j...07370/abstract

Well, I didn't mean to get carried away on this, and could discuss it for at least another hour, but unless the readers want to know more, I'll quit here... (for now).