There is no definitive easy way to diagnose pd.
There are the obvious motor symptoms plus micrographia and dry skin plus cognative symptoms like anxiety and inability to concentrate.
Usually a MRI scan and other tests may be used to rule out other possibilities like MND.
A DAT scan will give a good indication that there is pd present but is not infallible and some people have had clear scans and yet pd is still given as the diagnosis.
You may be put on medication or left to wait dependant on the severity of your symptoms and the way your neuro decides to treat your pd.
When you are medicated a favourable reaction is a strong indicator of pd, however, some pwp are given pills without adequate explanation of how to use them and this can cause further delays or confuse the dx further.
Generally though diagnosis is confirmed by progression of the symptoms and the medication working effectively.
Realising this is the key to managing your pd. Neuros unfortunately dont possess a tool that tells them what is going on in a pwp brain / body, they rely on feedback. With so many variables that can affect the way your medication works it is wise to get as informed as you can be and to find a neuro you can communicate with and who considers all factors before increasing your dose.