Packed red blood cell transfusion affecting phosphatidylethanol concentration

Introduction: Toxicologists are often called upon to interpret results of drug testing. Phosphatidylethanol is a biomarker sensitive for ethanol consumption within the previous one to four weeks and is commonly used in monitoring for alcohol abstinence in organ transplant candidates. Phosphatidylethanol is stable in stored units of packed red blood cells and has been shown to create “false positive” or iatrogenically elevated phosphatidylethanol concentrations after blood transfusion. Methods: In this prospective observational study, 50 subjects receiving one unit of packed red blood cells transfusion had their pre- and post-transfusion whole blood phosphatidylethanol concentrations measured using whole blood samples in EDTA vacutainers obtained within 24 hours of transfusion. Phosphatidylethanol was measured using liquid chromatography-tandem mass spectrometry with a 15% coefficient of variance. Pre- and post-transfusion hemoglobin and hematocrit were also measured. Results: Four (8%) subjects had an increase in phosphatidylethanol from “negative” (<20 ng/mL) to “positive” (>20 ng/mL) after transfusion. Six (12%) total subjects had any increase in phosphatidylethanol concentration beyond the coefficient of variance with a maximum increase of 51 ng/mL. No subjects had a decrease in phosphatidylethanol beyond the coefficient of variance. Discussion: This study adds to the evidence that patients receiving blood transfusions may have iatrogenically elevated phosphatidylethanol concentrations, even with a single unit of packed red blood cells. Conclusion: Phosphatidylethanol concentrations should be interpreted with caution if a patient has recently received a blood transfusion.