Testing related diagnoses should be viewed with a bit of skepticism, I think. I worked in test prep for five years, and our [high end] clientele had quite a way of paying their way to various diagnoses that granted extended time on the P/SAT, ACT, or whatever. (And in case you're curious, colleges are unable to view whether a student took the SAT under extended time conditions or not.)

That said, "exam anxiety" might be a new one to try in the college admissions racket.