To get a reliable diagnosis, you need a psychiatrist who is an expert on autism/Asperger's. Another AS person, which knows about his AS since many years and has met other AS people or read biographies and medical studies on AS, would probably be able to make a diagnosis as well, but he isn't licensed to give an official one, of course.
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Let come what will, I'll try it on,
My condition can't be worse;
And if there's money in that box,
'Tis munny in my purse.