Thats right. Because of the hefty costs of the GC/MS, Only the drug panel(s) that have tested non-negative on the initial assay screen will undergo the confirmation GC/MS.

And if youre worried about the GC/MS because of its lower (numerically) cutoff threshold, dont be. Even though their cutoff thresholds numerically differ, a 50 ng assay screen is functionally equivalent to the 15 ng GC/MS. For more info, read post #7 of this thread:
http://boards.cannabis.com/drug-test...d-testing.html