Thank you for that.
My father just died of Parkinson's. (Or at least, with it, but it was causing more and more serious issues.) I've probably got a decade before I would show any symptoms at all.
Meantime, I've been doing my best to be generically active and healthy -- I still run marathons, eat reasonably well, moderate alcohol, no smoking, etc. (Dad didn't smoke, either -- though there are rumors that nicotine might actually help.)
So this test would probably become commercially available right about the time I'd start taking it.