Did you pass the home test with the first urination of the day? If so, then you will have no problem passing the lab test. The faintness of a line has no affect on the validity of the test. Even synthetic urine will produce a faint line. The GC/MS will not be used first in the testing process. This test is only used to confirm a positive test result after the initial drug screen, which will be an Immunoassay. The Immunoassay is practically the same as any home dip test or cup test that you can buy at you local pharmacy or Walmart.

If you didn't use the first void of the day, then I would suggest picking up another home test and doing so.