Alcohol Biomarkers in Post-Liver Transplant Patients

Patients who have a positive PEth will be asked to have a confirmatory test performed 10-14 days after a positive result (PEth >20ng/ml). The rationale for this procedure is to determine the test retest reliability of this marker and as well as being able to correlate levels of drinking with changes in biomarker levels over time. There is limited information on the length of time PEth levels remain elevated in transplant patients after drinking episodes. Hypothesis H.1. PEth will have a significantly higher "area under the Receiver Operating Characteristic (ROC) curve" in a sample of post-transplant patients who report any alcohol use in the past 30 days compared to the control group. H.2. PEth will have a significantly higher "area under the ROC curve" in a sample of post-transplant patients who report daily alcohol use of >40 grams/day (three drinks/day) in the past 30 days compared to the control group. H.3. PEth will have a significantly higher "area under the ROC curve" in a sample of post-transplant patients who report heavy episodic drinking (>60 grams of alcohol, eight or more occasions in the past 30 days) compared to the control group. H.4. PEth levels will be <20 ng/ml in the control sample of 50 post transplant patients who do not have a history of alcohol dependence or alcohol related liver disease. H.5. The test-retest reliability of PEth will be >0.90.