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The standard THC test is a one-step rapid, qualitative immunoassay, a biochemical test
that measures the level of a substance in a biological liquid, typically serum or urine,
using the reaction of an antibody or antibodies to its antigen. The assay takes advantage
of the specific binding of an antibody to its antigen for the detection of
tetrahydrocannabinol compounds (11-nor-THC-9-Carboxylic Acid) in urine.
The cutoff concentration for a positive result in an immunoassay test is 50 ng/ml as
recommended by the Substance Abuse and Mental Health Services Administration
(SAMHSA) and NIDA. The cutoff for GC-MS and DOT is 15 ng/ml.