The GC/MS cutoff limit is 15 ng, but dont let this worry you. Even though their cutoffs numerically differ, a 50 ng Imnmunoassay is functionally equivalent to the 15 ng GC/MS. Their cutoffs numerically differ because the 50 ng I/A, being a non-selective methodology, recognizes all 31 metabolite concentrations combined while the GC/MS, a selective and more accurate methodology, recognizes only one metabolite concentration (THC-COOH).

THC enters the body in its ingested form, metabolized by the body, and exits the body as 31 different metabolite concentrations. The most prevalent of these 31 metabolite concentrations is the THC-COOH metabolite concentration.
In order to test negative on the I/A, the whole combination of the 31 metabolite concentrations must register below 50 ng.
In order to test negative on the GC/MS, only that one metabolite concentration (THC-COOH) must register below 15 ng. The cutoff has to be set at a lower numerical value to make the two types of tests functionally equivalent.
Burnt Toast Reviewed by Burnt Toast on . Home Test - Line or infamous Ghost Line? Possible Preemployment UA coming this week or next. I have been clean for 18 days. I am 5'9, 205, about 15 lbs overweight. Slow to medium metabolism and my job and commute don't leave much time for exercise. Before that I was toking about a gram a week, for the last year or so. I would make it last, small bowls lol. I home tested yesterday morning with my first void of the day. I got a very very faint line. Wondering if I should be thinking about a mild dilution effort. If the test is Rating: 5