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Frequently Asked Questions About Ethyl Glucuronide (ETG)

02/01/2007

1. What is Ethyl Glucuronide (EtG)?
Ethyl glucuronide (EtG) is a minor metabolite of ethanol (ethyl alcohol). It is formed in vivo as a consequence of alcohol exposure. A small fraction (approximately 0.02%) of any ethanol in the bloodstream is conjugated in the liver with glucuronic acid to form ethyl glucuronide. This compound is excreted in the urine. The applications of EtG as a marker of ethanol ingestion have been extensively described in peer-reviewed scientific literature.

2. Does SAMHSA (HHS) approve laboratories for EtG testing?
No, SAMHSA - HHS accreditation is only applicable to those workplaces that must perform testing under specific federal guidelines. This testing is for 5 drug classes including: PCP, Marijuana, Cocaine, Amphetamines and Opiates in urine. No other drugs (including alcohol or EtG) in urine are covered under current SAMHSA laboratory accreditation guidelines. However, SAMHSA has issued an Advisory that discusses EtG that was published in the September 2006 Substance Abuse Treatment Advisory, Volume 5, issue 4. This publication may be found by clicking here

3. How does NMS Labs assure the accuracy of testing for EtG?
All testing at NMS Labs adheres to the highest standards. As such, NMS Labs has an extensive quality assurance/ quality control program that provides for both internal and external oversight of its EtG testing procedures. These include:

  • Participation in a proficiency program specific for EtG run by ARVECON GmbH (Germany)
  • NMS LABS internal quality assurance program includes blind proficiency samples
  • Use of a validated analytical method utilizing state-of-the-art technology (LC-MS-MS)
  • Application of stringent procedures satisfying the high standards of our accrediting agencies

4. How are reporting limits chosen for EtG?
Ethyl glucuronide is a unique metabolite of ethyl alcohol. Any amount that is present in a urine specimen is indicative of in vivo exposure to ethanol. The lower the cutoff that is applied the longer the detection window will be for EtG. Interpretation of the EtG result may require an interview of the donor by a licensed physician who is trained to treat patients with alcoholism.

5. How long after drinking can EtG be detected?
The answer to this depends, among other things, on how much alcohol an individual has drunk and what reporting limit for EtG is being used. Among persons who are not alcoholics participating in controlled drinking studies, ethanol has been detected in urine samples for up to 2 days after drinking approximately the equivalent of six 12 ounce glasses of beer. EtG has been measured in urine samples for up to 80 hours after heavy ethanol exposure.

6. Can NMS LABS detect EtG in hair and blood?
NMS LABS currently does not offer routine testing of blood or hair for EtG. Journal article publications do indicate that the presence of EtG in these matrices can be detected.

7. What are the benefits of EtG over traditional urine alcohol testing?
EtG testing offers a longer time period for detection after the consumption of ethyl alcohol, as compared to direct testing for ethyl alcohol in urine. Based on the current body of knowledge, the presence of EtG is a specific indicator of ethyl alcohol (ethanol) exposure. Due to specimen collection and storage factors, fermentation in a urine sample may lead to false positives for ethanol since glucose and yeast may be present in the urine. Since EtG is created during the metabolism of ethanol, there is no currently known means for a positive EtG result to arise due to EtG formation in the collected sample.

8. Have there been any reports of false negatives or false positives in your laboratory or in controlled studies?
NMS Labs is unaware of any false positive analytical findings produced in our laboratory, and is quite confident that no more specific analytical method is currently available than the internally standardized LC/MS/MS procedure used in our facility.

EtG is known to degrade in the presence of the glucuronidase enzymes. Glucuronidases may occur in a urine sample due to the presence of certain bacteria such as E. Coli. Glucuronidase is also a constituent of blood. Therefore if blood or certain bacteria is present in a urine sample, EtG may degrade over time and a false negative finding could result. The chemical system to manufacture ethyl glucuronide from ethanol is not normally present outside of the body, and to date there have been no reports of EtG formation in collected urine samples.

As mentioned above in question 4, any positive finding must be considered in light of additional information including the possible sources of alcohol exposure, including e.g. alcohol-containing products other than alcoholic beverages. Please see the next question for a related discussion.

9. Are there any reports of medications, hand sanitizers, mouthwashes, etc that can cause positive EtG results?
EtG is produced whenever an individual is exposed to ethyl alcohol containing products that get in to the bloodstream; tests for EtG cannot determine the source of ethanol. For example, two studies were performed to evaluate the effect of alcohol-containing mouthwash on the appearance of ethyl glucuronide (EtG) in urine. In the first study, 9 volunteers were given a 4 oz. bottle of mouthwash, which contained 12% ethanol. They gargled with the mouthwash at intervals over a 15-minute period that utilized all 4 oz. All of their voided urine samples were collected over the next 24 hours. It was noted by all participants that the exposure was very uncomfortable and they would not want to repeat the experiment. Several participants complained of an excessively dry mouth at the end of the experiment. A total of 39 post exposure urine samples were provided. Of these, there were 20 that were greater than 50 ng/mL, but less than 100ng/mL; 12 were greater than 100 ng/mL, but less than 200ng/mL; 5 were greater than 200 ng/mL, but less than 250ng/mL; 3 were greater than 250 ng/mL, but less than 300ng/mL; and one was > 300 ng/mL (345 ng/mL). The peak concentrations were all within 5 hours after the exposure. This study demonstrated that excessive use of alcohol-containing mouthwash over a relatively short period of time can result in measurable EtG results greater than 250 ng/mL.

In the second study eleven participants gargled 3 times daily for 5 days. The first morning void was collected. Sixteen of the 55 submitted samples contained EtG concentrations of greater than 50 ng/mL. All of them were less than 120 ng/mL. These studies show that incidental exposure to mouthwash containing 12% ethanol, when gargling according to the manufacturers’ instructions, can result in urinary EtG values greater than 50 ng/m, but less than 120ng/mL.

10. NMS Labs currently utilizes LC/MS/MS technology. Are you considering using a less expensive Enzyme Immunoassay technology?
Not at this time. We are currently unaware of any commercially available immunoassay kit that supports the accurate detection of EtG with the sensitivity or specificity that is required for this type of analysis.

11. How long is EtG stable in a voided urine sample?
EtG has been shown to be stable for at least two weeks at room temperature when there is no glucuronidase activity in the sample. EtG is reported to be stable in frozen urine samples for at least one year.

12. Has EtG testing been presented as evidence in court?
Yes, EtG testing has been presented as evidence in court and other legal hearings. In this regard, EtG testing has been subjected to, and passed, scientific admissibility standards in several cases (Frye hearings).


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