Evaluation of a commercial LC-MS/MS assay for the quantification of ethyl glucuronide in urine for alcohol intake monitoring

Abstract

Background: A commercially available in vitro diagnostics (IVD)-approved mass spectrometric assay for the quantification of ethyl glucuronide (EtG) and ethyl sulfate (EtS) in urine (RECIPE Chemicals+Instruments GmbH, Munich, Germany) was verified for monitoring of recent alcohol intake after transplantation. Methods: For sample preparation, 50 μL of urine sample was mixed with an isotope-labeled internal standard solution. After centrifugation, 5 μL of the supernatant was analyzed by LC-MS/MS in a total run time of 3 min. An API 6500 tandem mass spectrometer (AB SCIEX, Toronto, Canada) combined with a Shimadzu UFLC system (Duisburg, Germany) was applied. Results: The limits of quantification for the commercial assay were 0.07 mg/L for EtG and 0.03 mg/L for EtS in urine. The coefficient of variation for both analytes was lower than 7% (within-day) and 15% (between-days). Accuracy ranged between 101 and 144% for samples from an external quality assurance program. The comparison of the commercial test kit and an established LC-MS/MS method showed a very good agreement for EtG (r=0.96) and EtS (r=0.97) over a broad urine concentration range. Conclusions: The commercial IVD-certified LC-MS/MS assay is suitable for the analysis of EtG and EtS in human urine[0] to assess recent alcohol intake in transplant monitoring.