Hair ethyl glucuronide concentrations in teetotalers: Should we re-evaluate the lower cut-off?

Aims: Ethyl glucuronide in hair (hEtG) can be used to assess the retrospective consumption of alcohol. A lower cut-off of 7 pg/mg hair in the 0-3 cm proximal scalp hair segment has been used for repeated alcohol consumption in the previous three months. While a concentration below this cut-off is stated not to contradict self reported abstinence, it is often used to assess whether an individual has remained abstinent in the period prior to hair sampling. Here, we address hEtG concentrations in alcohol consuming individuals and critically evaluate this cut-off value. Methods: Ten individuals remained abstinent from alcohol for 12 weeks. A lock of hair was cut before the start of the study, and the regrown hairs were cut after twelve weeks of abstinence. Hair EtG concentrations were measured both at baseline and after 12 weeks of abstinence. Study compliance was assessed by urine analysis every 2-3 days by liquid chromatography-tandem mass spectrometry with a lower limit of quantification (LLOQ) of 0.1 mu g/mL. HEtG concentrations were assessed in the first 3 cm hair using gas chromatography-tandem mass spectrometry with an LLOQ of 0.2 pg/mg. Results: At the beginning of the study, participants had hEtG concentrations ranging between