MedTox Lab Test. Help?

[sic1231]

I was sent to the hospital by my employer for a drug test yesterday. I'm worried they're going to skip the initial immunoassay test, since it appears the tests ordered are GC/MS confirmation tests with reduced cutoff levels.
One of the test codes is 149. The description of this test code on the test catalog portion of the MedTox website (MEDTOX : Test Catalog) reads:
"Quantitative result is marijuana metabolite measured as 11-nor-delta-9-carboxy-THC (carboxy-THC) by gas chromatography with mass spectrometry (GC/MS). Results are reported to limit of quantitation of the assay." I'm not sure if I should take this as meaning there's an assay first, or just the GC/MS test.
The top of the form I received reads "Non-Regulated 5 Part Drug Testing Custody and Control Form" with a MedTox logo. The test ordered are '149 THC', '831' coc, '9376 opi', and then it has an additional box that says other without a barcode beneath.
I'm very curious if anybody can put my mind at ease or offer some insight? I think I'd beat a 50 ng/ml cutoff but I'm not sure about a 15 or lower.
Also, what is the average amount of time to hear back from an MRO if a result is positive?
Thanks in advance.

sic1231 Reviewed by sic1231 on 10-08-2010. MedTox Lab Test. Help? I was sent to the hospital by my employer for a drug test yesterday. I'm worried they're going to skip the initial immunoassay test, since it appears the tests ordered are GC/MS confirmation tests with reduced cutoff levels. One of the test codes is 149. The description of this test code on the test catalog portion of the MedTox website (MEDTOX : Test Catalog) reads: "Quantitative result is marijuana metabolite measured as 11-nor-delta-9-carboxy-THC (carboxy-THC) by gas chromatography with Rating: 5

[Burnt Toast]

An assay will be performed first and if the sample fails that, THEN the GC/MS will be performed on the drug(s) that failed the assay. It would be way too costly to use the GC/MS as the primary methodology.


Dont let the differing cutoff levels freak you out. Although their cutoffs numerically differ, a 50 ng assay is functionally equivalent to the 15 ng GC/MS. Their cutoffs differ because the assay recognizes all 31 metabolite concentrations combined, while the GC/MS recognizes only 1 metabolite concentration.

THC enters the body in its ingested form and exits the body as 31 different metabolite concentrations. The most prevalent metabolite concentration is the 11-nor-delta-9-carboxy-THC (aka "THC-COOH") concentration.
In order to test negative on the assay, the combination of all 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.

[sic1231]

An assay will be performed first and if the sample fails that, THEN the GC/MS will be performed on the drug(s) that failed the assay. It would be way too costly to use the GC/MS as the primary methodology.


Dont let the differing cutoff levels freak you out. Although their cutoffs numerically differ, a 50 ng assay is functionally equivalent to the 15 ng GC/MS. Their cutoffs differ because the assay recognizes all 31 metabolite concentrations combined, while the GC/MS recognizes only 1 metabolite concentration.

THC enters the body in its ingested form and exits the body as 31 different metabolite concentrations. The most prevalent metabolite concentration is the 11-nor-delta-9-carboxy-THC (aka "THC-COOH") concentration.
In order to test negative on the assay, the combination of all 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.

thanks a lot for the info.
do you know if water is/can be considered a sample adulteration or substitution? or if the lab can distinguish between a person drinking excess water or adding water to their sample? i'm trying to get an idea of what result i could expect back after pouring some water into a lab sample to dilute it.

[Burnt Toast]

thanks a lot for the info.
do you know if water is/can be considered a sample adulteration or substitution? or if the lab can distinguish between a person drinking excess water or adding water to their sample? i'm trying to get an idea of what result i could expect back after pouring some water into a lab sample to dilute it.

Drinking large amounts of water leads to the sample being ruled "diluted" due to the creatinine level dropping below 20 mg/dL. A urine sample with a creatinine level between 2 - 20 mg is ruled diluted. Creatinine levels less than 2 mg are ruled "substituted" (aka "not consistant with human urine"). Adding water to a urine sample can easily cause the creatinine to nosedive to this range so watch your step. Under DHHS and DOT regulations, a retest under direct observation is in order if the creatinine level is between 2 - 5 mg

[sic1231]

geez. i really hope it doesn't fall below 2 then. it sounds so low, though. like there would have to be very little human urine in the specimen to drop below that.