Good point. There's no test for ADHD that's a 100% definitive test... like a blood test for a vitamin deficiency, for example. You fill out rating scales and it's very subjective. At least with kids, they have multiple people do the scales so they can see if the raters agree with each other, which gives more confidence in the ratings.
OCD and anxiety are strongly correlated with ADHD, so my opinion is that it would be worth trying the meds to see if those other issues improve at all. It'll give you some more information to go on.