You need to understand that the toxicology tests you're planning on running would start out in the same way as they do in bicycle racing and soccer, both of which are heavily tested in Europe and it's a constant process. Although I don't think there's much difference at the top, I'd have to say that the French and Swiss labs seem to be at the top of their game, with the US behind them.
The US tends to do sports testing in private labs, rather then state labs. Most of Europe does it in state labs, with little use of private labs. There's two aspects of testing: protocols and ability to determine results. You hear about the protocol constantly, and you automatically start thinking two samples, so the protocol is pretty good. There's been some big scandals in sports over the past few years where one sample was dirty, and no second sample, and the athelete getting away with it because of that.
Lance Armstrong, among others, has greatly contributed to the improved quality of toxicology tests for drug use. But one of the things Lance Armstrong shows is that you have to have some idea of what to test for. If the drug is something that is normally tested for, I would expect the Italian labs to pick it up. If the drug is an exotic and not commonly known, then it's hit or miss, regardless of where you are.
Mistakes happen. Bad labs exist. (See the Massachusetts problems.) But for the norm, mistakes aren't very common.
Best of luck,
Jim Clark-Dawe