While many neurologists and patients have been able to plainly see that PD (symptom constellation and disease progression) vary within the patient population, we have yet to scientifically validate clear subtypes. And, that still remains the case. The "three groups" are loosely defined and there are experts in the field that still disagree with the observations and specific descriptions of such subtypes. That is why it is said that further work is needed. It’s not clear additional subtypes will be described and it’s not clear that these early classes will be completely validated. But, everyone agrees that if we can validate the subtypes it will be extremely useful.

Debi