Recently I reviewed two urine tests from two residential clients that were positive for opiates. The drug testing provider confirmed these opiate positive results with follow-up tests utilizing Gas Chromatography/Mass Spectrometry (GC/MS). The quantitative GC/MS test was also positive for opiates but found both urine samples to contain fairly low levels of morphine and other opiate alkaloids. One of the urine specimens contained 0.15 micrograms/milliliter (µg/ml) of morphine and the other 0.3 µg/ml. Urine toxicology is routinely ordered for residential clients when they return from off site dental appointments or lab tests. Both clients were in treatment for alcohol and marijuana dependence with no history of opiate abuse and were doing well in our residential program. Neither exhibited clinical signs of being under the influence of any drugs, and denied any use while off site.
I contacted our testing provider’s toxicologist for more information and was told that the lab attributed morphine urine levels of under 5.0 µg/ml to be food-source contamination. Studies have confirmed that foods containing poppy seeds can result in a positive urine test for opiates.1, 2 Some cakes, cupcakes and bagels can contain enough poppy seeds to produce a positive urine tests when no opiates were abused. This is known as a false-positive opiate urine test.
Prior to 1998, the US threshold level for a positive opiate urine test was a morphine concentration greater than 300 nanograms/ml (ng/ml) or 0.3µg/ml. Those levels were changed to concentrations greater than 4000 ng/ml for morphine and 2000 ng/ml for codeine in response to the recognition that poppy seed contamination could indeed result in false-positive opiate test at that level. 1 This is 13 times greater than the amount that would have resulted in a positive urine test for opiates prior to 1998! The International Olympic Committee (IOC) set their threshold for morphine at 1000 ng/ml and will re-examine any disputed positive opiate test upon request.2 A nanogram is equal to 1000 micrograms so these levels are equivalent to 4.0 µg/ml and 2.0 µg/ml in the US and 1 µg/ml for the IOC.
Our clients’ urine tested positive for morphine with concentrations of only 0.15 and 0.3 µg/ml. These levels are well below the current threshold concentrations established for identifying use of opiates and clearly seemed to have resulted from food-source contamination. On the other hand, if one of these clients did use opiates and then remained abstinent several days previous to being tested, the low levels of opiates in the urine could actually be a positive indication of that use since body metabolism of the abused opiate would result in low residue urine concentrations several days after use. In this latter scenario, attributing low concentrations of opiates in the urine tests to food-source contamination would be a false-negative test for opiates in the urine and could contribute to continued abuse resulting in an eventual relapse to addiction. Unfortunate and unwarranted consequences result from misinterpreting low opiate concentrations of a false-positive urine test as a positive indication of drug abuse when it actually resulted from food-source contamination. But, equally unfortunate consequences can result from misinterpreting low opiate urine concentrations as a negative test if a urine specimen is collected after a sufficient length of time had lapsed since abuse of an opiate drug - a false-negative test.
We rely on a process known as a Therapeutic Positive to address this and other urine drug testing dilemmas. The Therapeutic Positive process brings the primary counselor and/or our program’s medical review officer and the client together to review the results of a positive drug test without providing the detail of the low concentration of the drug. The client is asked to explain why their urine contained the substance. This process provides an opening for the client to admit to a recent slip or drug exposure. If an admission is made, it is only used therapeutically to intensify the treatment process and develop strategies to avoid future interruptions to their recovery efforts. It is never used punitively to catch a client in a lie that could result in discipline or banishment from treatment. If the client adamantly denies use, and their treatment participation/performance validates this claim, program staff then works with the testing lab’s toxicologist to explore potential causes of a potential false-positive test.
Foods ingested prescription and non-prescription medications, illnesses, cosmetics and even personal hygiene products should be considered as possible sources for a false-positive test. In the two cases presented here, both clients ate a poppy seed muffin while waiting to be seen for their medical tests which were off-site.
Several years ago, I worked with a client who had tested cocaine positive due ingestion of Mate De Coca, a tea that contains coca leaves.3,4 Hemp oil is sometimes added to foods and it will result in a false-positive THC or marijuana test.5
In addition to food-source contamination, biologic processes and medications can result in questionable urine testing results. Sequestration and subsequent release of drugs from body fat can result in a marijuana or PCP urine “spike” which is another form of a false-positive test. The urine of diabetics have fermented into ethanol resulting in false-positive tests of alcohol consumption.6-9 A person’s hydration status and some disease states can impact urine creatinine which may be misinterpreted as a purposeful attempt to dilute urine and evade detection of drug abuse. The problem of false-positive ethanol test due to urine fermentation may have been partially addressed by the recent development of ethyl glucuronide (EtG) testing. EtG is only produced by the liver when alcohol is ingested. However, ethanol can also enter the body via other products such as food cooked with wine, mouthwash, or hand sanitizers and could result in false-positive tests. EtG testing better addresses false-negative tests because ethanol remains in urine for up to 80 hours after drinking whereas an ethanol level of 0.08 (legal limit for DUI violation) will result in no measurable levels of alcohol 5.33 hours after the last drink.10
Many prescription and non-prescription medications can complicate urine drug testing. Ibuprofen (Advil®, Motrin®, et. al.) is reported to cause both false-positive and false-negative (at high doses) THC or marijuana urine tests.11 Vicks® inhaler and nasal spray have resulted in false-positive urine tests for methamphetamine and Ecstasy. Dextromethorphan, found in cough and cold medications has been misidentified as morphine or other opiates. Antibiotic medications like amoxicillin or ampicillin have been misidentified as cocaine in some tests. An ongoing, growing and referenced list of many other medications and even illnesses that have been reported to result in false-positive urine tests for abused substances can be accessed on line at:
Darryl S. Inaba, PharmD., CADC III
- Meadway C, George S and Braithwaite R (1998). Opiate concentrations following the ingestion of poppy seed products – evidence for ‘the poppy seed defense’. Forensic Science International, 96:29-38.
Kaczorowski M (2008). The poppy seed defense: scientifically sound? McGill Sci Undergrad Res J, 3(1):40-41.
Jenkins AJ, Llosa T, Montoya I, Cone EJ (1996). Identification and quantitation of alkaloids in coca tea. Forensic Sci Int., 77(3):179-89.
elSohly MA, Stanford DF, elSohly HN (1986). Coca tea and urinalysis for cocaine metabolites, J Anal Toxicol, 10(6):256.
Kwong TC (2008). Handbook of drug monitoring methods: therapeutics and drugs of abuse. Humana Press, New York, NY.
Sulkowski HA, Wu AH, McCarter YS (1995). In-Vitro production of ethanol in urine by fermentation, J Forensic Sci. 40(6):990-3.
Saady JJ, Poklis A, Dalton HP. Production of urinary ethanol after sample collection, J Forensic Sci, 38(6):1467-71.
Logan BK, Jones AW (2000). Endogenous ethanol ‘auto-brewery syndrome’ as a drunk-driving defence challenge, Med Sci Law, 40(3):206-15
Gruszecki AC, Robinson CA, Kloda S, Brissle RM (2005). High urine ethanol and negative blood and vitreous ethanol in a diabetic woman: a case report, retrospective case survey, and review of the literature, Am J Forensic Med Pathol, 26(1):96-8.
Skipper GE, Weinmann W, Thierauf A, Schaefer P, Wiesbeck G, Allen JP, Miller M, Wurst FM (2004). Ethyl glucuronide: a biomarker to identify alcohol use by health professionals recovering from substance use disorders, Alcohol Alcohol, 39(5):445-9.
Brunk SD (1988). False negative GC/MS assay for carboxy THC due to ibuprofen interference. J Anal Toxicol, 12(5):290-1.