What is the EtG test


After the consumption of ethanol (alcohol), detoxification processes occur in the body in order to eliminate the alcohol from the body as quickly as possible. Alcohol is excreted in unchanged form directly through the lungs, skin and urine. There are the following specific analytical methods for detecting alcohol consumption:

  • Evidence of ethanol in the air you breathe (e.g. during police checks),
  • Detection of ethanol in the blood (blood alcohol level),
  • Detection of ethanol in the urine (screening).

In the body, alcohol is broken down in the liver by the enzyme alcohol dehydrogenase into acetaldehyde and then into acetic acid. The degradation rate shows considerable individual differences and averages 0.1–0.2 g / l / h. On average, women break down alcohol around 15 percent more slowly than men. Alcohol formed endogenously in the metabolism does not exceed 0.014 g / l (0.012 per mille) and can therefore be neglected.

In addition to the conversion of alcohol into acetaldehyde, the process of glucuronidation also leads to the formation of a direct alcohol metabolite in the liver:

ETG is also excreted in the urine, whereby this metabolic product, in contrast to the starting substance (ethanol), remains detectable in the urine over a longer period of time (approx. One to three days after alcohol consumption). For this reason, the evidence of ETG is mainly used in medicine to confirm the abstinence behavior of patients in the context of therapeutic alcohol cessation programs.

So-called "immunoassays" are usually used as an examination method in medical laboratories for the ETG determination in urine. These tests work with antibodies, which can also lead to undesired cross-reactions of these antibodies with non-relevant substances - in the case of ETG, cross-reactions with the sleeping pill chloral hydrate can occur.

For this reason, for sensitive, but always for forensic, questions, every positive ETG result must be confirmed with an analytically correct reference method (e.g. gas chromatography / mass spectrometry - GC / MS).