Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

DTHC
505331
FDS9R
57494
Drug of Abuse, Tetrahydrocannabinol Screen with GC-MS
Confirmation, Urine
Clinical Information: Marijuana is 1 of the most widely abused drugs in the United States. It is the
term for describing a leafy preparation of the plant Cannabis sativa used to produce psychic effects. A
common method for the consumption of marijuana is smoking. The primary component of marijuana is
delta-9-tetrahydrocannabinoid (THC). It is the concentration of THC that determines the potency of
marijuana. Following consumption of the drug, either by inhalation or ingestion, THC is rapidly
metabolized by the liver through 11-hydroxy-delta-9-THC to a series of polar metabolites, with
11-nor-delta-9-THC-alpha-carboxylic acid (THC carboxylic acid, THC-COOH) being the primary
metabolite. Approximately 80% of a dose of THC is eliminated during the first 5 days, with >65%
being excreted in feces and approximately 20% excreted in urine. Depending on assay sensitivity,
cannabinoid metabolites may be detected in the urine up to 10 days in occasional smokers and 30 to 40
days in chronic smokers.
Useful For: Detecting drug abuse involving delta-9-tetrahydrocannabinol (marijuana)
Interpretation: The metabolite of marijuana (THC-COOH) has a long half-life and can be detected
in urine for more than 7 days after a single use. The presence of THC-COOH in urine at concentrations
>15 ng/mL is a strong indicator that the patient has used marijuana. The presence of THC-COOH in
urine at concentrations >100 ng/mL indicates relatively recent use, probably within the past 7 days.
Levels >500 ng/mL suggest chronic and recent use. Chronic use causes accumulation of the THC and
THC-COOH in adipose tissue such that it is excreted into the urine for as long as 30 to 60 days from the
time chronic use is halted.
Reference Values:
Negative
EMIT cutoff concentration: 50 ng/mL
Positives are reported with a quantitative GC/MS result.
Clinical References: 1. Moyer TP, Palmen MA, Johnson P, et al: Marijuana testing-how good is
it? Mayo Clin Proc 1987;62:413-417 2. Baselt RC, Cravey RH: Disposition of Toxic Drugs and
Chemicals in Man. 3rd edition. Chicago, Year Book Medical Publishers, 1989
Drug Screen 9 Panel, Serum or Plasma-Immunoassay Screen
with Reflex to Mass Spectrometry Confirmation/Quantitation
Reference Values:
Drugs/Drug Classes Screen Cutoff
Amphetamines 30 ng/mL
Methamphetamine 30 ng/mL
Barbiturates 75 ng/mL
Benzodiazepines 75 ng/mL
Cannabinoids 30 ng/mL
Cocaine 30 ng/mL
Methadone 40 ng/mL
Opiates 30 ng/mL
Oxycodone 30 ng/mL
Phencyclidine 15 ng/mL
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