Dude, using gear while taking accutane is fucking STUPID. First of all, if you're taking it because you are naturally prone to acne, steroids will render it less effective. So you might have to take another course of accutane down the road. And secondly...yes, it will interfere with the bloodtest, accutane itself fucks your cholesterol, and any injectable will lower HDL (and increase LDL in many cases) even more than accutane alone which will make things worse. Accutane alone at 40mg per day decreased my HDL by about 30 points, and increased my LDL by more than that. My triglicerides went from 60 to 110 on accutane alone. I don't imagine taking supraphysiological doses of androgens would help those numbers very much. If you get a bad bloodtest, you won't be able to talk your doc into letting you take accutane. He will pull you off for AT LEAST 8 weeks if he's nice, most of them will not prescribe it to you again. Why risk that?
I have seen 2 threads in the past few weeks of dudes that were forced off of accutane because of bad bloodtest results - from taking gear.
The only thing you should even consider while taking accutane is perhaps a low dose of test. 250mg a week perhaps. More than that will have too big of an effect on HDL and cholesterol, and I have bloodtests to prove that. (I'm taking accutane right now)