Ethyl Glucuronide (EtG) is a specific marker in drug screens for recent alcohol consumption. It detects a byproduct of ethanol metabolism, showing alcohol intake even after alcohol has cleared the body. Its primary purpose is to monitor abstinence in situations like treatment programs or legal contexts.
Understanding Ethyl Glucuronide (EtG)
EtG is a direct metabolite of ethanol. When ethanol is consumed, the body processes it, primarily in the liver, through various enzymatic reactions. One reaction involves the conjugation of ethanol with glucuronic acid, forming EtG. This process makes EtG a specific indicator of alcohol exposure.
Unlike alcohol, which is rapidly eliminated, EtG remains detectable longer. This stability and extended detection window make EtG a preferred biomarker for assessing recent alcohol use. A small percentage of ethanol is metabolized into EtG and ethyl sulfate (EtS), which are readily excreted through urination.
EtG Detection Methods and Windows
EtG can be detected in various biological samples, with urine tests being the most common for recent alcohol use. A urine EtG test can detect alcohol consumption for up to 80 hours after intake. This extended detection window is useful for monitoring compliance.
Beyond urine, EtG can also be detected in hair and nails. Hair follicle tests can identify EtG presence from about a week up to three months after consumption. Nail samples can detect EtG for an even longer period, up to 120 days. These longer windows are particularly useful for assessing patterns of chronic alcohol consumption rather than just recent use.
Interpreting EtG Results and Considerations
A positive EtG test result generally indicates recent exposure to ethanol. However, the sensitivity of EtG tests means that even incidental exposure to alcohol from non-beverage sources can result in a positive test. Products like alcohol-based hand sanitizers, mouthwashes, certain over-the-counter medications, and some foods like sauerkraut or balsamic vinegar contain ethanol and can contribute to detectable EtG levels.
Interpreting EtG results requires careful consideration of the context and potential for incidental exposure. For instance, using alcohol-containing mouthwash can lead to EtG levels over 100 ng/mL, and repeated use of hand sanitizers has been linked to levels as high as 770 ng/mL. Therefore, some programs use different cut-off levels to distinguish between incidental exposure and intentional consumption. Common cut-off concentrations for urine EtG tests include 100 ng/mL, 250 ng/mL, or 500 ng/mL. Individuals undergoing EtG testing should avoid all products containing alcohol to prevent potential false positives.