Improved detection of ethyl glucuronide and ethyl sulfate in a pain management population using high-throughput LC-MS/MS

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Ethyl glucuronide (EtG) and ethyl sulfate (EtS) have been proposed as markers for detecting alcohol use because they exhibit extended excretion lifetimes when compared with ethanol; however, their presence is not considered as absolute proof of alcohol use. Two methods are currently used for the detection and quantitation of EtG: immunoassay and mass spectrometry. The purpose of this study was to provide more patient data to better compare the two methods. A retrospective diagnostic accuracy study was performed to compare the methods. EtS was also measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) as an additional comparative analyte. The investigators examined 4,287 sequential urines from pain patients to determine the incidence of alcohol use and the corresponding presence of EtG by immunoassay at a cutoff of 500 ng/mL. EtG and EtS were subsequently quantitated in all the urines using LC-MS/MS. A total of 794 samples were found positive by immunoassay, and these results were compared at three distinct LC-MS/MS cutoffs of 100, 500, and 1,000 ng/mL. The incidence of ethanol use in this population was found to be at least 12 percent. Approximately 30 percent of the samples screened by immunoassay as positive were confirmed to be negative by LC-MS/MS.