I have no idea that the Dat scan wasn't accurate. Although, in my case my MDS Neurologist diagnosed me a few months before I had the DaT scan. Both said I had Parkinson's.
Thank you for that information, and all the information that you talk about here. I found this really helpful.

For my husband, his symptoms were pretty classic: resting tremor in his hands, stiff arms, slow walking, hunched posture, festinating, falling, tiny handwriting and soft voice. He was diagnosed over the phone in early 2020 after I brought up the possibility with his GP several months earlier. The neurologist prescribed carbidopa-levadopa and Jim responded well to it (tremors stopped). When we were able to see her in person, she also watched him walk, tested strength and reflexes, etc. but the symptoms and his response to meds were really all she needed.

If there is doubt about the diagnosis, then there is a test they can do called a DaT scan that measures the amount of dopamine that the brain is producing. People with PD have significantly less dopamine. They may also do MRIs etc. to make sure the problem isn't because of brain injury or a stroke.