Direct alcohol biomarkers in blood samples of traffic offenders - correlation between blood alcohol concentration, ethyl glucuronide, and phosphatidylethanol

Abstract Background Phosphatidylethanol (PEth) and ethyl glucuronide (EtG) are established biomarkers of alcohol consumption, offering complementary insights into long-term and recent drinking behavior, as well as alcohol tolerance or dependence. This study examined the association between blood alcohol concentration (BAC), EtG, and PEth in blood samples collected predominantly in traffic-related forensic cases. Methods A total of 100 consecutive blood samples from 87 individuals submitted to the Institute of Legal Medicine in Munich for BAC determination were retrospectively analyzed for PEth and EtG. Samples originated from individuals in North Rhine-Westphalia, including mainly driving under influence (DUI), but also other alcohol-related offenses. BAC was measured via gas chromatography with a flame ionization detector and an enzymatic (ADH) method. PEth and EtG were quantified by validated LC-MS/MS procedures. Results Thirteen samples were excluded as post-drinking pairs from the same individuals, resulting in n = 87 samples included in the analysis. The study population was predominantly male (77%), with a mean age of 37 years. Most cases involved traffic offenders resp. drivers of motor vehicles, primarily cars. BACs were ≥ 1.1 g/kg in 73.5% and ≥ 1.6 g/kg in 47.1% of cases. EtG concentrations ranged from below cutoff to 8,627 ng/mL (median: 2,957 ng/mL), and PEth ranged from below the lower limit of quantification (LLOQ) to 1,520 ng/mL (median: 140 ng/mL). A moderate correlation was found between BAC and PEth ( r = 0.48, p < 0.01), and a strong correlation between BAC and EtG ( r = 0.79, p < 0.001). Both BAC and EtG concentrations increased with rising PEth categories, suggesting an association between acute alcohol intoxication and patterns of repeated consumption. Conclusion PEth findings 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.