Evaluation of N-acetyltaurine as an ethanol marker in human blood

- A validated LC-MS/MS method for the simultaneous determination of N-acetyltaurine and ethyl glucuronide in blood is presented.
- The application of N-acetyltaurine determination in blood was investigated in a drinking study with eight subjects.
- ROC curve analysis for blood alcohol concentration thresholds were performed for both biomarkers with forensic case samples.

To investigate the potential of N-acetyltaurine (NAcT) in blood as a biomarker for alcohol uptake, a previously published LC-MS/MS method for urine was modified to simultaneously detect NAcT and ethyl glucuronide (EtG). The method was applied in a drinking study and by analyzing 147 forensic case samples. In the drinking study, contrary to EtG, NAcT proved to be an endogenous substance, which was present at 22 ± 7 ng/mL (13-31 ng/mL) in the blood after 2 weeks of abstinence. A moderate increase in NAcT to 40 ± 10 ng/mL (27-57 ng/mL) was observed after drinking. Within 24 h, the NAcT concentrations declined to starting concentrations in seven out of eight subjects. Peak EtG concentrations (c¯max) of 445 ± 101 ng/mL (278-662 ng/mL) were reached. While EtG in blood can be used to detect alcohol consumption even if ethanol is already eliminated, some of the maximum NAcT concentrations after a single ethanol dose were in the range of endogenous levels detected prior to the start of drinking in other subjects. In the 147 blood samples, the following concentrations were found: blood alcohol concentration (BAC): 1.22 ± 0.95 g/kg (0-3.46 g/kg); NAcT: 37.8 ± 18.4 ng/mL (12.1-109 ng/mL); EtG: 1149 ± 1121 ng/mL (0-5950 ng/mL). ROC curve analysis for BAC thresholds at 0.8 and 1.6 g/kg were performed for EtG and NAcT. Due to the presence of endogenous NAcT levels resulting in a lower sensitivity and selectivity when compared to EtG, and due to a minor increase in concentration after alcohol uptake, the usefulness of NAcT as an alcohol biomarker in blood is very limited.

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