It was a simple 5 panel 50ng test, split sample, meaning they split the sample into 2 vials. They sent the test to the lab, and I got a call stating that I came up positive for THC. I'm completely devastated. This was my dream job and to make matters, worse, the lab said my concentration was 60ng! So I literally ALMOST passed, since the cutoff is 50ng.
Since the lab gave you a quantitative value, the urine sample was sent to the GC/MS, which has a cutoff threshold of 15 ng/ml.

The simple 5 panel 50ng test is an assay used for the initial screening. Assays are a "Pass/Fail" endeavor and have no ability to yield quantitative values. Thats when the confirmation GC/MS comes into play.

As adsad pointed out, the GC/MS is highly accurate and because of its accuracy, "false-positives" are eliminated when the urine sample is run through the GC/MS. The Mass Spec (MS) would indentify the exact substance present, so any excuses about poppy seeds, OTC meds, etc; would not float.

Because of the GC/MS's accuracy and its ability to quantify, being able to mount a successful challenge to its results is virtually futile. Keep this in mind if youre planning on challenging the results of sample vial 'A' by having vial 'B' tested.
Burnt Toast Reviewed by Burnt Toast on . Is Split Sample Re-testing worth it in this case? I used to smoke under a gram a day, but smoked almost daily. I stopped from about Feb 17th of this year for about 5 weeks. Around March 22nd I smoked again for about 2 weeks. I then stopped again for a little over 3 weeks before my test. In the meantime I did a full week natural "cleanse" (with vitamins and fiber), took Chlorella, Green Tea Extract, and exercised. I've lost almost 15 lbs (I was almost 260, 6'1" at my heaviest a couple of months ago, and now down to 245) so my metabolism is Rating: 5