Max, R E A L A X ! !! I have yet to find a urine test from Quest that does not start with the initial EMIT type screen. Then and only then, if the type test paid for includes a GC/MS for any possitive result in the initial, then and only then will a GC/MS be done. Last, to explain the differant cutoff levels. The initial assay EMIT type screen, screens out all 31 cannibiloid metabolites as well as any other metabolites from any other sources that are chemically a close enough match to fool the assay. ALL those metabolites must reach a volume of 50ng/ml and then the assay is possitive for marijuana. Then it is off to the GC/MS to try to confirm the initial assay's findings. The GC/MS is only targeting 1 metabolite of the original 31, THC-COOH/THCA. If the GC/MS finds a volume of 15ng/ml of the singular THCA, then the test is a confirmed possitive. THe 50ng/ml for the EMIT and the 15ng/ml for the GC/MS are roughly equall measures, so please don't be scared by a GC/MS. In fact, because some estamates are that as many as 20% of assay test possitives are false possitives, due to 'simmilar' metabolites being screened. The GC/MS conformation test should, IMHO, be welcomed. Hope that helps clear things up. N2