Ethyl glucuronide in hair and nail as a biomarker of alcohol consumption

Abstract

Background/aims Excessive use of alcohol may have many different harmful effects in health, legal and social perspectives. Underreporting alcohol consumption is a well-known phenomenon when subjects are asked to report their own alcohol use, and objective alcohol biomarkers are needed. The direct alcohol biomarker ethyl glucuronide (EtG) analysed in keratin matrices is used to evaluate the history of ethanol intake. The importance of correct interpretation of EtG concentrations in keratin matrices is underscored by the fact that it is used in clinical decisions, workplace testing and forensic medicine. As a general aim, we wanted to investigate opportunities and limitations of EtG as a biomarker for chronic alcohol consumption in hair and nails. More specifically, we aimed to investigate if decreased renal function may result in different hair EtG levels compared to healthy volunteers and implications of this. We also compared EtG levels in hair and nails among chronic excessive alcohol users and studied EtG elimination kinetics in nails. In addition, we aimed to investigate if hair EtG is stable during hair growth in an alcohol-abstinent period. Methods In paper I, we studied 41 patients with reduced kidney function and compared their hair EtG levels with levels found among 42 healthy volunteers, all reporting moderate alcohol use. In papers II and III we recruited patients from an alcohol rehabilitation clinic. In paper II, we included 40 patients and analysed EtG levels in both hair and nails at inclusion. In addition EtG was analysed in consecutive nail samples during the inpatient period. In paper III, we included 27 patients and for each patient we compared two consecutive hair samples collected with four-week abstinent intervals, analysing EtG concentrations in hair segments roughly representing the same alcohol consumption period. Results and conclusions In paper I, we found significantly higher hair EtG concentrations among patients with reduced kidney function compared to the healthy volunteers, even though the self-reported alcohol consumption did not differ significantly between the two groups. Consequently, interpretation of hair EtG levels among patients with decreased kidney function must be performed with caution to avoid misclassification of amounts of alcohol consumed. In paper II, we found higher EtG concentrations in nails compared to hair. EtG levels in both matrices correlated with self-reported alcohol consumption. EtG concentrations in nails disappeared faster than would have been expected from nail growth physiology. In paper III, we found decreasing hair EtG concentrations in most subjects during hair growth when comparing the two segments assumed to represent the same period of alcohol intake. Although there are uncontrolled factors present, the results support interpreting EtG in distal hair segments with caution. In summary, this thesis is a contribution to enhancing knowledge about the interpretation of EtG in hair and nails as a long-term alcohol biomarker. The findings of kidney function affecting hair EtG levels, kinetic data of EtG in nails and the alteration of EtG levels during hair growth might be of great importance for clinicians and toxicologists interpreting EtG levels in keratin matrices.