Ethyl glucuronide (EtG)
Ethyl glucuronide (EtG) is a metabolite produced by the body after consuming ethanol, primarily found in alcoholic beverages. It serves as a biomarker for detecting recent alcohol consumption, with testing typically performed on urine samples, though it can also be analyzed in hair or blood. EtG testing is highly regarded for its ability to indicate alcohol ingestion up to three to four days after consumption, making it particularly useful in settings that require strict adherence to sobriety, such as legal or employment scenarios.
Testing methods often involve immunoassay screens followed by liquid chromatography/mass spectrometry to ensure accurate results. However, it is important to note that EtG testing can yield false positives due to incidental exposure to alcohol-containing products or certain foods. Additionally, individual variations in metabolism can affect EtG levels in urine, complicating the interpretation of test results. The reliability of EtG tests has prompted discussions about their role in monitoring abstinence, emphasizing the need for comprehensive evaluation alongside other abstinence support methods.
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Ethyl glucuronide (EtG)
Introduction
Ethyl glucuronide (EtG) is formed by the body after being exposed to ethanol (typically in the form of alcoholic drinks) through a metabolic process known as glucuronidation. Ethyl glucuronide is used to determine, based on an individual’s urine sample, whether that individual has recently consumed alcohol. Studies have also shown that EtG testing may be effectively performed on samples of hair or blood, but this is not commonly done. Typical EtG testing protocols use immunoassay screens with liquid chromatography/mass spectroscopy to confirm apparent positive results. Testing for another ethanol metabolite, ethyl sulphate (EtS), can also be used to confirm EtG test results. EtG is more accurate in detecting alcohol ingestion for longer periods of time (within three to four days or eighty hours), which is ideal for zero tolerance and abstinence conditions as well as a means to detect alcohol relapsing. EtG testing can only identify consumed alcohol, rather than alcohol that is produced from fermentation, and can be used in conjunction with other drug testing analyses. Test results are typically produced thirty-six hours after the test is conducted.
Background
EtG test results have been used for employment purposes and as evidence in legal hearings. Moreover, ethyl glucuronide identification is essential in minimizing adverse drug reactions between opioids or sedatives and alcohol present in the bloodstream. Traditional urine tests were only effective for about twelve hours after alcohol consumption, whereas EtG testing is able to detect alcohol in the system for three to four days for heavy alcohol consumption.
When a person has consumed ethanol, it is excreted from the body in a number of ways. About 90 percent of it is converted to acetic acid or acetaldehyde; 5 to 10 percent is excreted directly in breath, sweat, or urine; and less than 0.1 percent is converted into EtG. The main benefit of testing for EtG over ethanol is that EtG remains in a person’s system longer. EtG testing employs liquid chromatography/mass spectroscopy to directly measure the amount of ethyl glucuronide present in urine samples. Moreover, toxicologists can use high performance liquid chromatography/mass spectrometry to interpret and indicate possible sources and interferences of ethyl glucuronide. Sometimes EtG testing can produce false positives, or the incorrect detection of alcohol in the system, from incidental exposure such as the consumption of alcohol-based food or exposure to alcohol-based products (such as mouthwash). Interpretation by certified toxicologists is essential in discerning whether the presence of EtG is actually due to direct consumption of alcohol.
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Alcohol and EtG testing using urine samples is not considered to fall under the jurisdiction of the Substance Abuse and Mental Health Services Administration (SAMHSA) and the United States Department of Health and Human Services (HHS), which provide guidelines for certain kinds of drug testing and oversee an accreditation process for laboratories performing those tests. By 2024, the SAMHSA-HHS accreditation board covered urine drug examinations for only five drug classes—phencyclidine (PCP), marijuana, cocaine, amphetamines, and opioids, which included codeine, heroin, morphine, oxycodone, oxymorphone, hydrocodone, and hydromorphone. Nongovernmental proficiency programs for EtG testing cover additional drub classes.
A varying amount of ethyl glucuronide in a urine sample can indicate alcohol consumption, although the cut-off value can vary depending on the laboratory protocol employed. It is important to note that lower cut-off values would require longer detection times. In addition, EtG test results require physician interpretation, especially for test-takers who have a history with alcoholism. How long EtG lasts in urine samples also varies depending on the individual; some people might convert higher percentages of alcohol into EtG than others, or might excrete it more quickly.
There are some issues with EtG testing. EtG testing takes a long time to provide results and often gives "false positives," or test results that incorrectly indicate the presence of ethanol. In addition, if the sample is stored at room temperature for too long, the EtG can degrade, resulting in a false negative.
Exposure to other products containing alcohol—such as mouthwash, breath spray, over-the-counter and prescription medications, and hand sanitizer—and the consumption of fermented or alcohol-containing food products—such as sauerkraut, balsamic vinegar, or vanilla extract—can produce a low-level EtG positive. In rare cases, a person’s body can create EtG without any alcohol exposure, especially if the person has diabetes. The excess glucose in a diabetic’s urine can ferment into ethanol and then be converted into EtG by microorganisms such as E. coli, resulting in a false positive.
EtG is stable in urine samples kept at room temperature for at least two weeks if there is an absence of glucuronidase activity, while frozen urine samples have been reported as stable for at least one year. Nevertheless, EtG testing should be employed in conjunction with other means to maintain alcohol abstinence, such as increased physical monitoring, case manager contact, and interviewing family members and employers.
Bibliography
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