Measurement of Urinary Ethyl Glucuronide Recommended for Monitoring Alcohol Abuse Following Liver Transplant

To determine how alcohol consumption should best be monitored, investigators at the University of Padua (Italy) evaluated the efficacy of several direct tests to detect alcohol in a target group of 121 liver transplant candidates and recipients. The investigators evaluated urinary ethyl glucuronide (uEtG), the Alcohol Use Disorders Identification Test for alcohol consumption (AUDIT-c), serum ethanol (sETOH), urinary ethanol (uETOH), and carbohydrate-deficient transferrin (CDT).

The Alcohol Use Disorders Identification Test (AUDIT-C) is an alcohol screen questionnaire that can help identify patients who are hazardous drinkers or have active alcohol use disorders (including alcohol abuse or dependence).

Ethyl glucuronide (EtG) is a metabolite of ethyl alcohol which is formed in the body by glucuronidation following exposure to ethanol, such as by drinking alcoholic beverages. It is used as a biomarker to test for ethanol use and to monitor or document alcohol abstinence in situations where drinking is prohibited. In addition to its use to monitor abstinence and detect drinking EtG also has potential for monitoring amount of alcohol use over time because it can be detected in hair and nails. A disadvantage of the test is that because EtG can be detected in samples at very low levels, it can also be positive after exposure to alcohol from nonbeverage sources, or incidental exposure, which can lead to innocent positives.

Serum and urine ethanol testing are linked to the fact that peak urine alcohol levels are reached 45 to 60 minutes after alcohol ingestion. At this time, urine alcohol levels are typically about 1.3 times greater than the corresponding blood alcohol concentration. This ratio is only valid during the elimination phase, which occurs after the blood alcohol level has peaked and is decreasing. Alcohol may be detected in the urine for one to two hours longer than it is detected in blood. The presence of alcohol in the urine indicates recent prior use, but may not correlate with the degree of intoxication observed at the time of testing.

Chronic alcoholism causes a transient change in the glycosylation pattern of the blood protein transferrin where the relative amounts of disialo- and asialotransferrin (carbohydrate deficient transferring or CDT) are increased over the amount of normally glycosylated tetrasialotransferrin. This recognition led to the use of CDT in serum as marker for chronic alcohol abuse. CDT typically normalizes within several weeks of abstinence of alcohol use. There are other causes of abnormal CDT levels, which include congenital disorders of glycosylation and other genetic and non-genetic causes of acute or chronic liver disease.

For the current study alcohol consumption was defined by a positive AUDIT-c or when it was confirmed by patient history in response to abnormal results. Alcohol consumption was found in 30.6% of patients. uEtG was found to be the strongest marker of alcohol consumption and showed a more accurate prediction rate of alcohol consumption when compared to CDT. The combination of uEtG with AUDIT-c showed a higher accuracy in detecting alcohol consumption when compared to the combination of CDT and AUDIT-c. Furthermore, uEtG was the most useful marker for detecting alcohol consumption in patients with a negative AUDIT-c.

"Assessing alcohol consumption is crucial in the selection of liver transplant candidates," said senior author Dr. Paolo Angeli, associate professor of medicine at the University of Padua. "Equally important is the ability to detect alcohol use in liver transplant recipients so early intervention for alcohol relapse can take place. It is vital that patients abstain from damaging drinking behavior following liver transplant to avoid graft loss or even death. When used together, uEtG and AUDIT-c provide an important tool in the management of transplant patients at risk for alcohol relapse."

The study was published in the May 2014 online edition of the journal Liver Transplantation.

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