Ethyl glucuronide in keratinous matrices as biomarker of alcohol use: A correlation study between hair and nails

- Evaluation of EtG concentrations in hair, finger- and toenails.
- EtG levels in hair and nails significantly and positively correlated.
- Higher concentrations present in finger- and toenails compared to hair.
- Nails as useful alternative to hair for monitoring of alcohol consumption.
- Preliminary cut-off values for EtG concentrations in fingernails proposed.

To quantify alcohol use, objective, specific and sensitive long-term alcohol markers are necessary. Ethyl glucuronide (EtG), a direct metabolite of alcohol, accumulates in keratinous matrices such as hair and nails, and is a specific and sensitive long-term biomarker for the detection of chronic alcohol consumption. So far, research has primarily focused on the detection of EtG in hair, and studies on its measurement in nails are scarce. In this article, we assessed EtG concentrations in hair, finger- and toenails from the same individuals in order to evaluate the direct correlation between the matrices. To this end, a total amount of 45 hair, 41 fingernail, and 13 toenail samples were collected from patients treated for alcohol use disorders at two psychiatric centers in Belgium. Samples were analyzed by gas chromatography-tandem mass spectrometry. Hair EtG concentrations ranged from 123 pg/mg for chronic excessive alcohol consumption, 59-123 pg/mg for moderate alcohol consumption, and <59 pg/mg for alcohol abstinence. In light of these results, nails may be a useful alternative to hair samples for monitoring of long-term alcohol consumption, e.g., in cases where hair is not available. Further studies are needed to establish cut-off values for EtG levels in nails.