Ethyl glucuronide in hair: a ten-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 assess long-term alcohol consumption by examining the distribution of EtG according to age, gender, recidivism, referral context, sampling region, hair length, and the impact of seasonality and the COVID-19 pandemic. Hair EtG concentrations were determined using HPLC-MS/MS, and samples were classified according to the Society of Hair Testing (SoHT) recommended cut-offs: EtG≤5 pg/mg (consistent with abstinence), 5<30 pg/mg (indicative of repeated alcohol consumption), and EtG≥30 pg/mg (indicative of chronic excessive alcohol consumption). A descriptive sensitivity analysis using SoHT cut-offs was performed to ensure 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 concentrations varied significantly by gender, age and referral context. Statistically significant differences were also observed among head, chest, axillary, and pubic hair samples. Higher EtG concentrations were detected in the proximal 3-cm segment of head hair compared to the 3-6 cm segment (p = 2.7353 × 10−42), as well as across seasons (p = 1.4591 × 10−14), with higher values during colder months. No measurable short-term population impact of COVID-19 was detected (p = 0.0980); however, a significant long-term effect was observed (p = 4.3000 × 10−6). Overall, despite considerable variability of EtG concentrations, this study provides robust evidence supporting the reliability of hair EtG testing and offers a comprehensive overview of long-term alcohol consumption trends in a monitored Italian population.