I don't think it will depend where I go, as Department of Transportation regulations differ from other regulations, I would imagine. For DoT testing, I would assume the same rules and regulations have to be followed.

It makes sense that if you pass the initial test, they most likely would not do any further testing, because everyone who really was clean would be subjected to this extra test, which costs extra money.

It seems like the confirmation test would be for failure confirmation, but I don't know that for sure.

Does anyone know what ratio you can realistically dilute to? I mean is it just as feasible to beat a 15 ng/mL cutoff as it is to beat a 50 ng/mL cutoff, if you continue to dilute?

I'm really hoping someone knowledgeable comments on this.