Abstract
Phosphatidylethanol is a direct alcohol biomarker for identifying alcohol misuse. It carries several advantages over other alcohol biomarkers, including a detection half-life of several weeks and little confounding by patient characteristics or organ dysfunction. The aim of this study is to derive an optimal phosphatidylethanol cut point to identify organ donors with alcohol misuse, and to assess the impact of alcohol misuse on organ allocation. Discrimination of phosphatidylethanol was evaluated using the area under the ROC curve from a mixed effects logistic regression model. Phosphatidylethanol had an area under the ROC curve of 0.89 (95% CI 0.80-0.98). A phosphatidylethanol cut point of ≥84 ng/mL provided optimal discrimination for the identification of alcohol misuse with a sensitivity of 75% (95% CI 52.9%-89.4%) and a specificity of 97% (95% CI 91%-99%), a positive predictive value of 82% (95% CI 59%-94%), and a negative predictive value of 95% (95% CI 89%-98%). In deceased organ donors who had been critically ill, phosphatidylethanol had good test characteristics to discriminate alcohol misuse. Other alcohol biomarkers performed poorly in deceased organ donors. Liver allocation was decreased in donors with alcohol misuse by proxy history, but not in those with phosphatidylethanol >84 ng/mL, revealing possible information bias in liver allocation.