I prefer the procedure from 20 years ago. Where ADHD was defined by having the systems, and then testing every other thing that it could be.
It took my son 2 months to be officially diagnosed. A real pain? Sure. But a heck of a lot better than the situation today where kids with chronic sleep deprivation are given an ADHD diagnosis, then sent home with a medication that masks the sleep deprivation while giving them insomnia.