The initial Immunoassay screen (as well as the home test) has a cutoff limit of 50 ng while the confirmation GC/MS has a cutoff limit of 15 ng.

But dont let the differing cutoffs worry you. Even though they numerically differ, a 50 ng I/A screen is functionally equivalent to the 15 ng GC/MS. For more info, read post #18 of this thread:

http://boards.cannabis.com/drug-test...ml#post2202713