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Lab Manual for Moffitt-Long and Mount Zion

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Tetrahydrocannabinol Screen, Urine

Item Value
Test Update Information Effective 01/14/2013, the platform used for the tetrahydrocannabinol immunoassay screen has changed from the Abbot Axsym to the Beckman UniCel DxC 800.
Approval req'd? No
Available Stat? Yes
Test code THC
Test group Cannabinoid
Performed by Parnassus Chemistry
In House Availability Test available 24 hours per day 7 days per week
Method Competitive enzyme immunoassay method (Beckman UniCel DxC800 analyzer) using G6PDH labeling
Container type Urine cup
Amount to Collect See preferred volume
Sample type Random Urine
Preferred volume 1 mL urine
Min. Volume 0.5 mL urine
Normal range Negative

Note: a negative result indicates that this class of drugs is not present, or they are present at a concentration below the cut-off concentration of 50 µg/L
Synonyms THC; marijuana; Tetrahydrocannabinol; cannabis; pot; Cannabinoids
Stability Refrigerated 7 days, frozen at -20C 2. weeks
Turn around times Stat 2 hours, Routine 4 hours
Additional information This immunoassay is only a screening test and is not definitive. Results cannot be used for medico-legal purposes.

A concentration of < 50 µg/L is considered negative by this test. A positive result is ≥ 50 µg/L and indicates the presence of this class of drugs.

Cannabis metabolites can be detected in urine up to 95 days after use.( From: Verstraete AG. Detection Times of Drugs of Abuse in Blood, Urine and Oral Fluid. Ther Drug Monit, 26(2) April 2004, 200-205)

False positive results may occur due to other cross reacting substances, however, positive results are NOT routinely confirmed by a second method. If confirmation of the test result is required, it is the responsibility of the physician to separately order a specific confirmatory test for the drug identified. False negative results are also possible, for example, with use of newer JWH compounds and other synthetic cannabinoids.

Click here for List of Cross Reactive Substances

Samples are held for 7 days. Contact laboratory at x 31667 to request confirmatory testing. Confirmation test code THCC.
LOINC code 18282-4
Last Updated 1/18/2013 12:05:02 PM
Entry Number 165
Lab Procedure Link Click here for Procedure

If you have additional questions regarding this test, please call: 415-353-1667

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