EVIDENCE LIBRARY
Can BAC, EtG and PEth Distinguish One Drinking Episode From Repeated Use?
An 87-person forensic sample linked higher BAC with higher EtG and PEth, but overlapping results, unknown drinking times and transport conditions limit individual drinking-history conclusions.
BAC, blood EtG and PEth provide different information, but their combination did not definitively separate one exceptional drinking episode from repeated use in an individual. A 2026 study of 87 forensic cases found group-level associations among the three measurements. Its cross-sectional design, overlapping values and sample-handling uncertainties limit stronger conclusions.
Three measurements with different meanings
Holzer and colleagues examined 100 consecutive blood submissions originally sent for alcohol analysis. Thirteen were second samples from the same individuals and were excluded from the main analysis, leaving 87 people. Seventy-six cases involved suspected DUI; the remaining 11 involved other suspected alcohol-related offenses.
BAC was reported as grams per kilogram of whole blood after the laboratory’s measurement and conversion procedure. EtG was measured in whole blood in ng/mL. PEth 16:0/18:1 was also reported in ng/mL. These are not interchangeable concentrations, and the study’s blood EtG values are not urine EtG results.
Ethanol reflects alcohol present when sampled. EtG is an ethanol metabolite whose concentration also depends on time since drinking and metabolism. PEth reflects ethanol-associated phospholipid formation and persistence, adding information about exposure beyond the immediate ethanol result. Neither biomarker directly measures driving impairment.
Associations in the overall forensic sample
In the results section, BAC correlated strongly with EtG, r = 0.778, and moderately with PEth, r = 0.497; both were statistically significant at p < 0.01. The median PEth concentration was 140 ng/mL. Thirty-five of 87 people had PEth at or above the study’s 200-ng/mL category.
Median BAC increased across PEth groups: 1.04 g/kg below 100 ng/mL PEth, 1.56 g/kg at 100 to below 200 ng/mL, and 1.93 g/kg at or above 200 ng/mL. These are group summaries, not a conversion formula from PEth to BAC.
The overlap is important. In the lowest PEth category, BAC ranged from zero to 2.11 g/kg. A lower PEth therefore did not rule out a high contemporaneous ethanol concentration. Conversely, one person with a negative ethanol result had measurable EtG and PEth.
What the DUI subset adds
The DUI subset contained 54 car cases, 11 bicycle or e-bike cases, six e-scooter cases, three moped cases and two motorcycle cases. Twenty-eight of the 76 had PEth at or above 200 ng/mL.
Among the 35 DUI cases with BAC at or above 1.6 g/kg, 54.3% had PEth at or above 200 ng/mL, while five had PEth below 100 ng/mL. These categories describe the researchers’ analysis. They should not be presented as universal legal thresholds or as a diagnosis of dependence.
The correlations in the DUI subset remained stronger for BAC–EtG than for BAC–PEth. This supports using the measurements to ask different temporal questions. It does not establish how much a particular driver drank, when the drinking began or whether alcohol caused a particular driving error.
Why a single episode was not ruled out person by person
The researchers lacked detailed drinking histories, timing of peak BAC and duration of intake. There was no prospective reference classification proving which participants had consumed alcohol only once after abstinence and which had repeated exposure.
Accordingly, the finding that higher PEth often accompanied higher BAC is consistent with repeated use in many cases, but it does not validate a perfect single-episode versus habitual-use classifier. The paper’s broader suggestion that isolated drinking accounts for only a minority of offenses goes beyond what these records can independently establish for each person.
The site’s PEth and reported drinking over 14 days addresses a different design for comparing a biomarker with drinking history.
Sample handling remains part of the interpretation
Samples were refrigerated at police stations but transported without temperature control. They were subsequently frozen for biomarker analysis. The authors acknowledged that PEth can form after collection when ethanol remains present, and inferred that cold-season transport probably limited this effect. Actual uncontrolled transport temperatures were not established for each specimen.
That uncertainty cannot be resolved merely by adding another biomarker. Case interpretation needs the collection time, storage and transport record, assay details and relevant drinking history. The site’s analysis of post-collection PEth formation discusses this separate preanalytical issue.
Primary source
Holzer A and colleagues. Direct alcohol biomarkers in blood samples of traffic offenders – correlation between blood alcohol concentration, ethyl glucuronide, and phosphatidylethanol. International Journal of Legal Medicine. 2026;140:2825–2832. https://doi.org/10.1007/s00414-026-03834-w.