cannabinoid in urine

Reference interval

• Not applicable

Principle

• immunoassays measure the major active component of Cannabis sativa (marijuana) delta-9-tetrahydrocannabinol (THC), metabolites, or both
• HPLC-MS or GC-MS provides a confirmatory test
• most commercial kits use antibodies directed towards 11-nor-delta-9-tetrahydrocannibinol-9-carboxylic acid, the most abundant metabolite (inactive)
• since THC is stored in adipose tissue, this metabolite may persist in the urine for several weeks after last use depending upon frequency & duration of use
• extremely low concentrations due to passive inhalations may be detected

The Urine Cannabinoid pack is used in the DuPont ACA discrete clinical analyzer to qualitatively screen cannabinoids in human urine. It is an adaptation of Syva's homogeneous enzyme immunoassay technique, EMIT. The reagents used in this methodology are matched lots of antibody reactive to delta-9-THC and the delta-9-glucose-6-phosphate dehydrogenase conjugate. The concentration of cannabinoids in the sample determines the amount of Delta-9-THC - glucose-6-phosphate dehydrogenase (THC-G6PD) conjugate that is bound to the antibody reactive to Delta-9-THC. The unbound conjugate catalyzes the oxidation of glucose-6- phosphate, with the simultaneous reduction of NAD to NADH, more rapidly than does the bound conjugate. The rate of increasing absorbance at 340 nm due to the increase in NADH is related to the concentration of cannabinoids in the sample by means of a calibration curve or a mathematical function.

Clinical significance

The urine cannabinoid assay is used to qualitatively screen cannabinoids in human urine. This test provides only a preliminary analytical test result. A more specific alternate chemical method must be used in order to obtain a confirmed analytical result. Gas Chromatography/Mass Spectrometry (GC/MS) is the preferred confirmatory method. Clinical consideration & professional judgement should be applied to any drug of abuse test result, particularly when preliminary positive results are used.

Specimen

Patient preparation: No special patient preparation is required.

Urine samples should be collected in clean, unbreakable, & leak proof containers. Freshly voided urine specimens should be used. If not analyzed immediately, samples should be stored refrigerated. Refrigerated storage exceeding 3 days, however, may result in positive samples with drug concentrations around 0.30 ug/mL assaying as falsely negative. Drug-free samples have not been observed to produce positive results following storage.

Samples should be within the pH range of 5-8. Samples with pH outside this range should be adjusted to this range by the addition of 1 N HCL or 1N NaOH before assaying. Specimens may be encountered that display high turbidity. It is recommended that these be centrifuged before analysis.

More general terms

• cannabinoid in body fluid
• urine toxicology

More specific terms

• cannabinoid in urine qualitative
• cannabinoid in urine quantitative
• carboxy-tetrahydrocannabinol in urine
• tetrahydrocannabinol in urine

Component of

• cannabinoid/creatinine in urine