What is EtG? Where does it come from?
EtG, or ethylglucuronide, is a byproduct of ethanol (alcohol that one drinks) and glucuronide a common biological compound made in the liver that binds various toxins and drugs in the body that allows them to be excreted in the urine. When someone drinks, even relatively small amounts of alcohol, EtG is formed and can be detected in the urine.
Why is urine EtG detection any better than a blood or breath alcohol test?
EtG can be found in the urine much longer than alcohol in the blood or breath. After a few drinks, EtG can be present in the urine up to 48 hours, and sometimes up to 72 or hours or longer if the drinking is heavier.
Can the EtG amount indicate how much alcohol someone has actually consumed (i.e. the number of drinks)?
Not really. While higher amounts of EtG might indicate larger amounts of alcohol consumption, the exact number is influenced by several factors: the amount and when it was consumed. The longer the time since consumption, the lower the EtG level (see above). Also, some people might convert more alcohol into EtG than others and/or excrete it more quickly. Finally, there is a maximum amount of EtG that can be measured, so drinking above that limit might not raise EtG more than can be detected (ceiling effect). It was designed to detect “any drinking”, not heavy drinking. If you wish to detect heavy drinking consider ordering %dCDT (see other information).
Why do you report EtG levels at two different cut-offs 100 ng/ml and 500 ng/ml?
We do this to provide complete information on which to base a sound clinical decision. EtG can be detected by our assay system at levels even below 100 ng/ml, but we build in a “margin of safety” so that at 100 ng/ml we are very certain that EtG is present, indicating even small amounts of drinking. However, there have been some reports in the literature, as well as concern raised in legal cases, that other sources of alcohol (e.g. mouthwash, hand sanitizer) might cause levels of EtG above 100 ng/ml to be detected in the urine. Although these situations are rare, and hard to replicate under controlled conditions, in those instances where a higher level of certainty is needed (forensic cases etc.) the clinician might want to use the 500 ng/ml cut-off.