Snozek Christine L H, Jannetto Paul J, Langman Loralie J, Kinard Theresa N
Department of Laboratory Medicine, Mayo Clinic Arizona, Phoenix, AZ, USA.
Department of Laboratory Medicine, Mayo Clinic Rochester, Rochester, MN, USA.
J Anal Toxicol. 2025 Sep 5. doi: 10.1093/jat/bkaf084.
Alcohol biomarkers including ethyl glucuronide (EtG) and phosphatidylethanol (PEth) are ordered frequently in clinical and forensic settings including solid organ transplantation. PEth provides a long detection window but can be insensitive to light drinking. In contrast, EtG and ethyl sulfate (EtS) can be elevated after light alcohol consumption and might complement PEth testing.
Urine EtG/EtS and whole blood PEth results were evaluated from all clinically-ordered testing between 2014-2024. PEth and EtG/EtS confirmation were performed by liquid chromatography tandem mass spectrometry at two reference laboratories, using cutoffs: Lab A, PEth 20 ng/mL, EtG and EtS 500 and 250 ng/mL; Lab B, PEth 10 ng/mL, EtG and EtS 250 and 100 ng/mL. Only Lab B performed EtG screening by immunoassay, using a 500 ng/mL cutoff.
PEth was positive in 1269 (15.6%) of 8131 samples, compared to 769 (6.7%) confirmed EtG/EtS positives from 11555 samples. EtG screening (n = 9668) was positive in 743 (7.7%) samples, of which 30 (4.0%) confirmed negative (false positives); the screen was indeterminate in 267 (2.8%) samples, 66 of which confirmed positive and 172 negative. Of 3132 paired PEth and EtG samples, 2887 (92.2%) were concordant, 224 (7.2%) were PEth-positive and 21 (0.7%) were EtG-positive. PEth was significantly more sensitive in paired samples (p < 0.001), even after accounting for potential confounders. Limiting testing to PEth would have correctly identified alcohol consumption in 331 of 373 (88.7%) instances versus EtG/EtS in 149 (39.9%), and reduced charges by >$720,000 USD.
PEth outperformed EtG/EtS in detecting alcohol consumption in a predominantly abstinent transplant population. Compared to PEth, EtG/EtS had lower overall positivity and poorer sensitivity in paired samples; additionally, EtG screening demonstrated false positives and indeterminate results. EtG testing provided little added value beyond PEth in this population, and did not warrant the increased cost of performing both tests.
