Chromatographic Analysis of Alcohol Biomarkers Reveal Drinking Patterns

Phosphatidylethanol (PEth) and ethyl glucuronide (EtG) are reliable markers that show whether someone has been drinking alcohol. They help reveal both long-term and recent drinking patterns, plus signs of tolerance or dependence. German researchers studied how blood alcohol levels connect with EtG and PEth in samples mostly from traffic-related cases, measuring blood alcohol using gas chromatography with a flame ionization detector (GC-FID) and an enzymatic (ADH) method, while PEth and EtG were quantified by validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) procedures. A paper based on their work was published in the International Journal of Legal Medicine.¹

Why Are EtG and PEth Useful for Assessing Alcohol Consumption in Driving Fitness Evaluations?

Accurately understanding a person’s drinking habits is very important in traffic medicine, especially when deciding whether someone is fit to drive under German licensing rules (§ 13 FeV). Traditional methods, such as asking people about their drinking, conducting interviews, or using indirect blood markers like γ-GT or CDT, are often unreliable because they can miss alcohol misuse or be influenced by inaccurate self-reporting.^2-4

In recent years, newer alcohol markers called EtG and PEth have become more useful because they can detect alcohol consumption more directly and accurately. EtG is a substance the body produces after drinking alcohol and can be measured in blood, urine, or hair. In blood, it mainly shows recent drinking within the past hours, depending on how much alcohol was consumed and how quickly the body processes it. Compared to urine testing, blood EtG is less affected by factors like hydration or kidney function, making it more reliable in forensic and legal settings.^2,4

PEth works differently. It is only formed in the body when alcohol is present and builds up in red blood cell membranes over time. Because of this, it can show repeated or long-term alcohol consumption over several weeks. One specific type, called PEth 16:0/18:1, is considered especially accurate and sensitive for detecting ongoing heavy drinking.^4,5

How Can PEth, EtG, and BAC Together Help Assess Drinking Behavior?

In this study, researchers looked back at 100 blood samples from 87 people that had been tested for PEtH and EtG at the Institute of Legal Medicine in Munich. Most of the people were from North Rhine-Westphalia and had been involved in alcohol-related incidents, mainly drunk driving. Thirteen samples were removed because they came from repeat tests taken shortly after drinking, leaving 87 samples for the final analysis. Most participants were men (77%) with an average age of 37. Traffic-related offenses made up most cases, mostly involving car drivers. Blood alcohol levels were at or above the legal limit in nearly three-quarters of the cases, and in about 42% they were more than twice the legal limit. EtG levels varied widely, while PEtH levels ranged from low to very high. The researchers found that higher PEtH levels were linked to higher EtG levels, especially in people with higher blood alcohol concentrations. This suggests that heavy drinking episodes may be connected to repeated alcohol use patterns.¹

“PEth findings,” write the authors of the paper,¹ “suggest that alcohol-related driving offenses often involve repeated or heavy alcohol consumption. Combined EtG, PEth, and BAC analysis offers a comprehensive approach to distinguish between single drinking episodes and habitual use and is particularly useful for evaluating isolated drinking after prolonged abstinence.”

The researchers point out that the exact amount and timing of alcohol consumption, peak blood alcohol levels, and when the incident ended were not known, making it difficult to fully interpret the PEth and EtG test results. In addition, the blood samples were kept refrigerated at the police station but later transported without temperature control during cold weather. Earlier studies have shown that PEth levels can increase in stored samples if alcohol is present, especially at room temperature. However, little to no increase was seen when samples were kept cold, so any changes in PEth levels during transport were likely minimal. Even with these limitations, however, the researchers believe that their study was unusual because it tracked multiple alcohol-related biomarkers in a series of real-world traffic offense blood samples — something rarely done and only possible with special approval from authorities in North Rhine-Westphalia.¹

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References

1. Holzer, A.; Neumann, J.; Stoever, A. et al. Direct Alcohol Biomarkers in Blood Samples of Traffic Offenders - Correlation Between Blood Alcohol Concentration, Ethyl Glucuronide, and Phosphatidylethanol. Int J Legal Med. 2026,DOI: 10.1007/s00414-026-03834-w
2. Skopp, G.; Mußhoff, F.Aktuelles zu Alkoholkonsum- markern bei forensischen und suchtmedizinischen Fragestellungen. SUCHT 2020, 66, 329–338. DOI: 10.1024/0939-5911/a000687
3. Thierauf, A.; Große Perdekamp, M.; Weinmann, W. et al. Alkoholkonsummarker Rechtsmedizin 2011, 21, 69–79. DOI: 10.1007/s00194-010-0729-6
4. Andresen-Streichert, H.; Müller, A.; Glahn, A. et al.Alcohol Biomarkers in Clinical and Forensic Contexts. Dtsch Arztebl Int 2018, 115, 309–315. DOI: 10.3238/arztebl.2018.0309
5. Jones, A. W. Brief History of the Alcohol Biomarkers CDT, EtG, EtS, 5-HTOL, and PEth. Drug Test Anal 2024, 16, 570–587. DOI: 10.1002/dta.3584