Sign in →

Test Code THCM 11-nor-Delta-9-Tetrahydrocannabinol-9-Carboxylic Acid (Carboxy-THC) Confirmation, Meconium

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

Carboxy-THC Confirmation, M

Specimen Type


Advisory Information

For chain-of-custody testing, order THCMX / 11-nor-Delta-9-Tetrahydrocannabinol-9-Carboxylic Acid (Carboxy-THC) Confirmation, Chain of Custody, Meconium.

Specimen Required

Supplies: Stool container. Small (Random), 4 oz (T288)

Container/Tube: Stool container (T288)

Specimen Volume: 1 g (approximately 1 teaspoon)

Collection Instructions: Collect entire random meconium specimen.

Reject Due To








Grossly bloody reject, Pink OK; stool, diapers

Specimen Stability Information

Specimen Type Temperature Time
Meconium Frozen (preferred) 28 days
  Refrigerated  21 days
  Ambient  14 days

Specimen Minimum Volume

0.3 g (approximately 1/4 teaspoon)

Day(s) and Time(s) Performed

Monday through Friday, Sunday; Varies

Analytic Time

2 days

Reference Values


Positives are reported with a quantitative LC-MS/MS result.

Cutoff concentrations

Tetrahydrocannabinol carboxylic acid (marijuana metabolite) by LC-MS/MS: 10 ng/g

Useful For

Detection of in utero drug exposure to marijuana (tetrahydrocannabinol) up to 5 months before birth

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

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


G0480 (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
THCM Carboxy-THC Confirmation, M 69007-3


Result ID Test Result Name Result LOINC Value
31863 THC 69007-3
31876 Interpretation 69050-3
31877 Chain of Custody No LOINC Needed

Clinical Information

Marijuana and other psychoactive products obtained from the plant Cannabis sativa are the most widely used illicit drugs in the world.(1) Marijuana has unique behavioral effects that include feelings of euphoria and relaxation, altered time perception, impaired learning and memory, lack of concentration, and mood changes (eg, panic reactions and paranoia).


Cannabis sativa produces numerous compounds collectively known as cannabinoids including delta-9-tetrahydrocannabinol (THC), which is the most prevalent and produces most of the characteristic pharmacological effects of smoked marijuana.(2) THC undergoes rapid hydroxylation by the cytochrome (CYP) enzyme system to form the active metabolite 11-hydroxy-THC. Subsequent oxidation of 11-hydroxy-THC produces the inactive metabolite 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH; carboxy-THC). THC-COOH and its glucuronide conjugate have been identified as the major end-products of metabolism. THC is highly lipid soluble, resulting in its concentration and prolonged retention in fat tissue.(3)


Cannabinoids cross the placenta, but a dose-response relationship or correlation has not been established between the amount of marijuana use in pregnancy and the levels of cannabinoids found in meconium, the first fecal matter passed by the neonate.(4,5) The disposition of drug in meconium is not well understood. The proposed mechanism is that the fetus excretes drug into bile and amniotic fluid. Drug accumulates in meconium either by direct deposition from bile or through swallowing amniotic fluid.(5) The first evidence of meconium in the fetal intestine appears at approximately the tenth to twelfth week of gestation, and slowly moves into the colon by the sixteenth week of gestation.(6) Therefore, the presence of drugs in meconium has been proposed to be indicative of in utero drug exposure during the final 4 to 5 months of pregnancy, a longer historical measure than is possible by urinalysis.(5)


The presence of 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid at 10 ng/g or greater is indicative of in utero drug exposure up to 5 months before birth.


No significant cautionary statements.

Clinical Reference

1. Huestis MA: Marijuana. In Principles of Forensic Toxicology. Second edition. Edited by B Levine. Washington DC, AACC Press, 2003 pp 229-264

2. O'Brein CP: Drug addiction and drug abuse. In Goodman and Gilman's The Pharmacological Basis of Therapeutics. 11th edition. Edited by LL Burton, JS Lazo, KL Parker. McGraw-Hill Companies Inc, 2006. Available at URL:

3. Baselt RC: Tetrahydrocannabinol. In Disposition of Toxic Drugs and Chemical in Man. Edited by RC Baselt. Foster City, CA, Biomedical Publications, 2008: pp1513-1518

4. Ostrea EM Jr, Knapop DK, Tannenbaum L, et al: Estimates of illicit drug use during pregnancy by maternal interview, hair analysis, and meconium analysis. J Pediatr 2001;138:344-348

5. Ostrea EM Jr, Brady MJ, Parks PM, et al: Drug screening of meconium in infants of drug-dependent mothers: an alternative to urine testing. J Pediatr 1989;115:474-477

6. Ahanya SN, Lakshmanan J, Morgan BL, Ross MG: Meconium passage in utero: mechanisms, consequences, and management. Obstet Gynecol Surv 2005;60:45-56

Method Description

Meconium is mixed with internal standard and broken down with acetic acid. The sample is then extracted with methanol and further processed by solid-phase extraction. The extract is analyzed by liquid chromatography-tandem mass spectrometry.(Unpublished Mayo method)