My son took a drug test last week. He was told he tested positive for thc, however, he does not do drugs. He requested a lab test be done. They told him his result was 34 with a 15 cut off for the screen on a gc/ms. Is it possible this is a false positive? Or did they even do a lab test at all?

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Originally Posted by chasen

my son took a drug test last week. he was told he tested positive for thc, however, he does not do drugs. he requested a lab test be done. they told him his result was 34 with a 15 cut off for the screen on a gc/ms. Is it possible this is a false positive? or did they even do a lab test at all?

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That is a very unusual set of numbers for THC.

Based on the cutoff, 15*, it was a urine test and that is the standard cutoff for THC in the confirmatory test, GC/MS. That makes sense so far.

However, a confirmatory test (GC/MS) is performed only if the initial assay (IA), is positive at 50* or above. A reading of 34* should not have registered on the IA and been returned as negative. Therefore not subjected to GC/MS.

GC/MS** is performed only in a laboratory. It is not a test that can be performed on site. Instrumentally, the test is very sensitive and precise but 34* is an extremely low reading for THC.

You and/or your son should request a copy of the test results. Both tests. With that information maybe we can figure this out. Once again, those are confusing numbers, one contradicting the other.


*nanograms
**Gas Chromatography/Mass Spectrometry