Ethyl Glucuronide in Hair: A 10-Year Overview.

This 10-year retrospective study evaluates hair ethyl glucuronide (EtG), a direct metabolite of ethanol, in a large Northern Italian cohort (N = 68,221 samples collected between 2013 and 2022). The analysis aimed to evaluate long-term alcohol consumption through the EtG distribution in terms of age, gender, recidivism, applicants, sampling region, sampling length, and the impact of seasonality and the COVID-19 pandemic. Hair EtG was determined by HPLC-MS/MS, and samples were classified according to the Society of Hair Testing (SoHT) recommended cut-offs: EtG ≤ 5 pg/mg (does not contradict abstinence), 5 < EtG < 30 pg/mg (repeated alcohol consumption), and EtG ≥ 30 pg/mg (chronic excessive alcohol consumption). A descriptive sensitivity analysis using SoHT cut-offs was performed to allow international comparability. The percentage (%) of hair samples classified as repeated or chronic excessive alcohol consumption was 13.6% (N = 9,281) and 5.6% (N = 3,818), respectively. EtG values significantly varied with gender and age as well as referral context. We observed statistically significant differences in EtG concentrations recorded in head, chest, axillary, and pubic hair samples. Significantly higher EtG values were detected in 3-cm proximal head hair versus the 3- to 6-cm proximal segment as well as across seasons, with a higher concentration in colder months. Conversely, no measurable short-term population impact of COVID-19 was revealed by hair EtG, whereas a significant long-term influence was highlighted. Overall, despite a large variability of EtG concentrations, this study provides robust evidence of the reliability of hair EtG testing and offers a comprehensive overview of long-term alcohol consumption trends in a monitored Italian population.