How do you know what your readings were? Home tests, being assays, lack the ability to yield quantitative values.
That means you will be taking an initial assay screen with a 50 ng cutoff limit. If the sample fails the initial assay, then it undergoes the confirmation GC/MS with a 15 ng cutoff limit and a quantitative value will be provided. Samples that pass the initial assay screen wont undergo the confirmation test.
Even though their cutoffs numerically differ, a 50 ng assay is functionally equivalent to the 15 ng GC/MS. The numbers differ because the assay recognizes all 31 metabolite concentrations combined, while the GC/MS only recognizes one metabolite concentration (THC-COOH).
For more info on this, read my post in this thread:
http://boards.cannabis.com/drug-test...test-help.html