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Test ID: THCU Carboxy-Tetrahydrocannabinol (THC) Confirmation, Random, Urine

Reporting Name

Carboxy-THC Confirmation, U

Useful For

Confirmation of drug abuse involving delta-9-tetrahydrocannabinol (marijuana)

Specimen Type

Urine


Advisory Information


1. For situations where chain of custody is required, a Chain-of-Custody Kit (T282) is available. For chain-of-custody testing, order THCX / Carboxy-Tetrahydrocannabinol (THC) Confirmation, Chain of Custody, Random, Urine.

2. Additional drug panels and specific requests are available. Call 800-533-1710 or 507-266-5700.

3. If urine creatinine is required or adulteration of the sample is suspected, order, ADULT / Adulterants Survey, Random, Urine.



Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Collection Container Tube: Plastic urine container

Submission Container/Tube: 10 mL tube

Specimen Volume: 10 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.

Additional Information:

1. No specimen substitutions.

2. STATS are not accepted for this test.


Specimen Minimum Volume

5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 14 days
  Frozen  14 days
  Ambient  72 hours

Reference Values

Negative

 

Cutoff concentration:

Carboxy-THC- by GC/MS <3.0 ng/mL

Day(s) and Time(s) Performed

Monday through Friday; Varies

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

80349

G0480 (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
THCU Carboxy-THC Confirmation, U 20521-1

 

Result ID Test Result Name Result LOINC Value
2497 Carboxy-THC- by GC/MS 20521-1
21186 Carboxy-THC Interpretation 69050-3
21187 Chain of Custody 77202-0

Clinical Information

Delta-9-tetrahydrocannabinol (THC) is the active agent of the popularly abused street drug, marijuana.

 

Following consumption of the drug, either by inhalation or ingestion, it is metabolized to a variety of inactive chemicals, one of them being delta-9-tetrahydrocannabinol carboxylic acid.

 

In almost all medico-legal cases and in screening of employees, or when the patient adamantly denies THC use and the immunoassay test is positive, confirmation of the result by gas chromatography-mass spectrometry (GC-MS) is required.

Interpretation

The presence of tetrahydrocannabinol carboxylic acid (THC-COOH), a major metabolite of delta-9-tetrahydrocannabinol, in urine at concentrations greater than 15.0 ng/mL is a strong indicator that the patient has used marijuana.

 

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 greater than 100.0 ng/mL indicates relatively recent use, probably within the past 7 days. Levels greater than 500.0 ng/mL suggest chronic and recent use. Chronic use causes accumulation of 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.

Clinical Reference

1. Disposition of Toxic Drugs and Chemicals in Man. Tenth edition. Edited by RC Baselt. Biomedical Publications, 2014

2. Langman LJ Bechtel LK, Meier BM, Holstege C: Chapter 41:  Clinical Toxicology. In Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Edited by N Rifai, AR Horvath, CT Wittwer. Sixth edition. Elsevier, 2018, pp 832-887

Analytic Time

3 days

Method Name

Gas Chromatography-Mass Spectrometry (GC-MS) Confirmation with Quantitation

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-General Request (T239)

-Therapeutics Test Request (T831)

Mayo Clinic Laboratories | Therapeutics Catalog Additional Information:
mml-THC, mml-substancemonitoring