What is PEth?
Phosphatidylethanol (PEth) is an alcohol marker measured in the blood. PEth is formed when ethanol is present in the body, and the marker is used to assess alcohol consumption over the past few weeks to just over a month. It is not used to determine whether a person is under the influence of alcohol at the time of sampling, nor can it establish exactly when or how much alcohol was consumed.
How long does PEth remain in the blood?
When a person stops consuming alcohol, PEth levels gradually decrease. The half-life is often cited as approximately 4–10 days, though there is significant individual variation. The duration for which PEth remains detectable depends on factors such as the initial level, previous consumption patterns, and individual biological differences.
Consequently, an elevated level may persist for several weeks after the last alcohol intake, especially if the initial level was high. A general half-life cannot be used to reliably calculate when a specific individual's PEth level will fall below a certain threshold.
How is a PEth value interpreted?
Based on nationally harmonized interpretation thresholds, the following guidelines apply:
- <0.05 µmol/L: A value below 0.05 indicates no alcohol consumption or only sporadic consumption.
- 0.05–0.30 µmol/L: A value between 0.05 and 0.30 indicates alcohol intake ranging from low to high levels. A completely risk-free level of consumption cannot be established at the individual level.
- >0.30 µmol/L: A value above 0.30 indicates extensive and regular alcohol intake.
The interpretation thresholds are approximate—there is no exact relationship between the amount of alcohol consumed and the measured PEth value. The same level of alcohol consumption can result in widely varying PEth values in different individuals. Therefore, results must always be assessed with regard to individual variations, the timing of the sample collection, and any previous test results.
What does a change in PEth value mean?
A decrease in PEth values across repeated tests may indicate reduced or ceased alcohol consumption. Conversely, a rising value may suggest continued or increased consumption. Because the formation and breakdown of PEth vary between individuals, it is not possible to determine exactly how much or when someone has been drinking based solely on the change in value.
PEth in medical assessments and driver's license cases
PEth results can form part of the basis for medical assessments, such as those concerning driver's licenses. A single PEth value should not be evaluated in isolation. In driver's license cases, a comprehensive assessment is made based on current regulations and medical evidence, which may include repeated test results and other relevant information.
