Sorry I can't answer your question, but I wanted to thank you for answering one of mine about the faint line, I have been showing a faint line for 2 weeks as of today, my first faint line showed up arround 30 days after quiting, and now I am at 48 days and still getting a faint line. Good luck and please let us know the outcome of your lab test.

And if you are interested in my progress read my thread:
every day smoker over 30 years