Formation of phosphatidylethanol and ethylglucuronide after low to moderate alcohol consumption in volunteers with a previous three-week alcohol abstinence

Phosphatidylethanol (PEth) is only formed when ethanol is present in blood. This direct alcohol marker has been widely discussed, including the minimum amount of ethanol being necessary to form as much PEth as to exceed the threshold of 20 ng/mL in previously PEth negative subjects. In order to corroborate hitherto existing results, a drinking study including 18 participants after a 3-week alcohol abstinence was performed.They consumed a pre-calculated amount of ethanol to reach a blood alcohol concentration (BAC) of at least 0.6 g/kg. Blood was drawn before and periodically seven times after alcohol administration on day 1. Blood and urine were also collected the next morning. Dried blood spots (DBS) were prepared immediately from collected venous blood. BAC was determined by head space gas chromatography and the concentrations of both PEth (16:0/18:1, 16:0/18:2 and five additional homologues) and ethyl glucuronide (EtG) were analysed using liquid chromatography-tandem mass spectrometry.Out of 18, 5 participants had concentrations of PEth 16:0/18:1 above the threshold of 20 ng/mL, and 11 out of the 18 subjects had concentrations between 10 and 20 ng/mL. In addition, four persons had PEth 16:0/18:2 concentrations above 20 ng/mL the following morning. All test subjects tested positive for EtG in DBS (≥ 3 ng/mL) and urine (≥100 ng/mL) upon 20-21 h after alcohol administration.By combining both a lower cutoff of 10 ng/mL and the homologue PEth 16:0/18:2, the sensitivity to detect a single alcohol intake after a 3-week abstinence increases to 72.2%.