Phosphatidylethanol (PEth) is considered as specific biomarker of alcohol consumption. Due to accumulation after repeated drinking, PEth is suitable to monitor long-term drinking behavior. To examine the applicability of PEth in "driving under the influence of alcohol" cases, 142 blood samples with blood alcohol concentrations (BAC) ranging from 0.0-3.12‰ were analyzed for the presence of PEth homologues 16:0/18:1 (889 ± 878 ng/mL; range <LOQ to 5400 ng/mL) and 16:0/18:2 (355 ± 315 ng/mL; range <LOQ to 1440 ng/mL) by LC-MS/MS. With receiver operating characteristic analysis, PEth thresholds were evaluated to differentiate moderate and excessive alcohol consumption with acceptable sensitivity and specificity in accordance with the 1.6‰ BAC limit. With a threshold of 700 ng/mL for PEth 16:0/18:1, prolonged excessive alcohol consumption was detected in 65.9% of drunk drivers with a BAC ≥ 1.6‰ and in 31.6% of the samples with a BAC < 1.6‰. Similar results were obtained for PEth 16:0/18:2 with a threshold of 300 ng/mL. Both criteria, PEth 16:0/18:1 and PEth 16:0/18:2, were conform in the evaluation of drinking habits in 88.7% of blood samples. These results show the possibility to detect prolonged excessive alcohol consumption, even if the BAC is below the legal threshold of 1.6‰ for driving aptitude assessment. As a consequence, concentrations of PEth 16:0/18:1 ≥ 700 ng/mL and of PEth 16:0/18:2 ≥ 300 ng/mL may be considered as indicators for the necessity of driving aptitude assessment in addition to BAC.
Keywords: Alcohol biomarker; Driving under the influence (DUI); LC-MS/MS; Phosphatidylethanol.