Phosphatidylethanol (PEth) is a group of direct, non-oxidative alcohol biomarkers. The abnormal phospholipid PEth is only formed within the human body when alcohol is present. Thereby, the enzyme Phospholipase D (PLD) catalyzes the biotransformation (phase II reaction) of phosphatidylcholine to form PEth. Until today, about 48 PEth species (analogs) have been identified in human blood. PEth 16:0/18:1 and PEth 16:0/18:2 are the two most abundant analogs of PEth and often measured together.

PEth concentrations provide information about a subject’s drinking behavior. This information is much needed in various situations, such as alcohol withdrawal treatment settings, driving aptitude assessments, issuing gun licenses, family law, and organ transplant settings. For the classification of drinking habits, generally, a lower and an upper threshold are applied for PEth 16:0/18:1, allowing the classification of analytical results into three groups:

–>Teetotalers (below the lower threshold)

–>Moderate drinkers (above the lower threshold, and below the upper threshold)

–>Excessive consumers (above the upper threshold)

Dependent on the country of analysis, these thresholds and the classification of the groups may vary. Generally, the lower PEth threshold is used to distinguish between light or no alcohol consumption and significant alcohol consumption. The upper threshold is intended to distinguish between significant alcohol consumption and heavy alcohol consumption.

As PEth is not stable in liquid blood (unless stored at -80ºC), it is preferentially measured using Dried Blood Spots (DBS) which show better analyte stability. DBS is a specimen sampling technique, whereby small volumes of blood (10-20 µL) are sampled on cotton filter paper and left to dry. In contrast to sampling blood by venipuncture, DBS have the advantage that minimally invasive sampling is possible (e.g. by a finger-prick).