You ask a good but difficult question. When I was supporting someone with aspergers at their P.T. session, this very question came up. And she told me you don't really see adults going to get tested because of the stigma attached to autism and as an adult they have found a successful way to cope in society.
That was a number of years back. With no one commenting on your post, I couldn't help but recall that conversation.
Sorry I didn't really give you an answer.

Hi Skimbleshanks
Depending on your age there's a possibility you could have had autism all your life but be high functioning and therefore it wasn't diagnosed earlier. There are many different levels and types of autism. It's only in the last few decades since sufficient research and testing has been done that diagnosis has become more readily available. Anyone who was a child in the 1960's, 70's or 80's, who may have mild to moderate autism or asperger's, might have been put in a standard school system and learnt to cope and never been diagnosed.

Has the neurologist suggested further testing for autism? Did she give any indication of what type she thought you might have? I have not heard of anyone developing autism as an adult (that's not to say it's not possible) but you say your onset started about 3 yrs ago - this would suggest an acqired disease or reaction to something. Also the question about exposure to heavy metals may be in relation to Neurotoxicity, depending on what condition the doctor was trying to diagnose.

Sorry this probably leaves you with more questions than answers. Are you due to see the Neurologist again? Did you get a written report from the neuro appt. - if not - requesting a copy might give you more info. Maybe you could ask for specifc answers next time she asks such vague questions. Don't be anxious about the doctor asking you the autism question - if she didn't give you a definitive diagnosis then she is just considering any and all possibilities.
All the best in your search for answers.

Hi SkimbleShanks

I had a chat with my partner about this - she is a psychologist with expertise in working with children who have developmental delays.

Her comment was, that while adult diagnosis of Autism Spectrum Disorder is unusual, it can happen.

Her suggestion was that seeing a psychologist who knows about ASD as well as your neurologist is a plan which is worth considering (as bluesfan has implied).