Background: At present, recent ethanol consumption can be routinely detected with certainty only by direct measurement of ethanol concentration in blood or urine. Because ethanol is rapidly eliminated from the circulation, however, the time span for this detection is in the range of hours. Several new markers have been proposed to extend the detection interval, but their characteristics have not yet justified their use in routine clinical practice. We therefore investigated three new markers and compared their kinetics and sensitivities: (1) fatty acid ethyl esters (FAEEs) in serum, (2) ethyl glucuronide (EtG) in urine, and (3) the ratio of 5-hydroxytryptophol to 5-hydroxyindole acetic acid (5-HTOL/5-HIAA) in urine.
Methods: Seventeen healthy men participated in a drinking experiment. Blood and urine samples were collected twice daily on three consecutive days and once daily on days 4 and 5. Ethanol concentration was determined by gas chromatography, FAEE levels, by gas chromatography with mass spectrometry, EtG concentration, by liquid chromatography-tandem mass spectrometry, and 5-HTOL/5-HIAA ratio, by high-performance liquid chromatography.
Results: The peak serum ethanol concentrations of the subjects ranged from 5.4 to 44.7 mmol/liter (mean +/- SD, 30.1 +/- 9.1 mmol/liter). In the case of the serum ethanol determination, 100% sensitivity was reached only immediately after the end of the drinking experiment, and in the case of FAEE levels and 5-HTOL/5-HIAA ratio, it tested for 6.7 hr after the end of the ethanol intake. Thereafter, these latter parameters declined until 15.3 hr (FAEEs) and 29.4 hr (5-HTOL/5-HIAA), subsequently remaining in a stable range until 78.5 hr without further decrease. In contrast, EtG concentration showed 100% sensitivity until 39.3 hr and thereafter decreased, falling to below the limit of quantification of 0.1 mg/liter at 102.5 hr.
Conclusion: After moderate drinking, EtG in the urine proved to be a superior marker of recent ethanol consumption in healthy subjects. This is because EtG is a direct ethanol metabolite, it occurs in the urine only when ethanol has been consumed, and its sensitivity remains at the level of 100% for 39.3 hr.