This common expression is  so so wrong:
He is diagnosed with topsicitis.
The direct object "he" is wrong for that verb, as is the indirect object "topsicitis" for the preposition "with."
Compare the truly correct expression:
His disease is diagnosed as topsicitis by the doctor with the aids of advanced techniques.
Â
Well, wrong things do win. Â But this is one of those that will never stop being wrong no matter how right it has become, which it long long has.
The first two dictionaries I looked at include diagnosis of the patient as well as the disease. I'm afraid it's a done deal. Wrong and never are perhaps a little strong in something as flexible and evolutionary as word usage.