Ethanol Biomarker Testing and Challenges.

Area of Science:

• Clinical Chemistry
• Forensic Toxicology
• Biomarker Analysis

Background:

• Ethanol biomarkers, ethyl glucuronide (EtG) and ethyl sulfate (EtS), are crucial for distinguishing alcohol use from abstinence in clinical and forensic settings.
• Accurate interpretation of EtG and EtS testing is vital for critical decisions like transplant eligibility and professional licensure.
• Variability in testing methodologies and reporting cutoffs can impact the reliability of these important biomarkers.

Purpose of the Study:

• To evaluate trends in the testing of EtG and EtS over a seven-year period.
• To assess how different laboratories perform EtG and EtS testing and the comparability of participant results.
• To identify areas for improvement in assay performance and reporting standards for ethanol biomarkers.

Main Methods:

• Analysis of the College of American Pathologists ethanol biomarker proficiency testing survey data from 2013 to 2019.
• Evaluation of trends in methodology, reporting cutoffs, and participant performance for qualitative and quantitative EtG testing.
• Assessment of trends for quantitative EtS testing using mass spectrometry and immunoassay techniques.

Main Results:

• Significant lack of consensus observed in reporting cutoffs for both EtG (10–1000 ng/mL) and EtS (10–1500 ng/mL).
• While median EtG and EtS values aligned with targets, individual participant results showed wide variability.
• Approximately 10% of all results were deemed unacceptable, with mass spectrometry showing high variability in accuracy.

Conclusions:

• Despite many participants performing well, insufficient consensus on reporting cutoffs and a consistent failure to meet survey standards by some laboratories were noted.
• Development of standardized guidelines for assay performance and reporting is recommended.
• Such guidelines would significantly benefit both laboratories conducting the tests and the end-users relying on the results.