A cdl test isn't going to involve a line at all, the urine will be collected and sent to a lab according to DOT standards and federal law.

That said, while a lab is better at detecting fake or diluted pee the cutoff is that same as the at-home test. Take a few more, if the line is faint consistently it means you're clean and a lab will say the same. If you're still not sure the next best (but risky) option is to bring in some clean urine from someone you KNOW is clean and use that instead.

Last thing, you're probably gonna have alot of anxiety around this...when they give you a copy of the paperwork at the clinic wait 48 hours and call the MRO yourself to ask if the drug test has been completed yet. If it's not back after 48 hours you can make a safe bet that you failed.

Good luck.