It has been reported that some patients have been misdiagnosed with Alzheimer's, when in fact the correct diagnosis in their specific case was Parkinson's Disease.
Parkinsons disease should be diagnosed by a neurologist. There is no single test used to confirm diagnosis. The diagnosis is based on a physical test, review of medical history, and a neurological examination. Lab tests may be required to rule out other dieases. The condition can not be cured but there are medications available to control the symptoms with high success.