(P-BC-42) False-positive Elevation of a Marker of Ethanol Abuse, Phosphatidylethanol, Following Single Unit Red Blood Cell Transfusion

Background/Case Studies: Phosphatidylethanol (PEth) is a phospholipid-ethanol metabolite synthesized on the erythrocyte membrane. Quantitative liquid chromatography tandem mass-spectrometry assay (LC-MS/MS) whole blood PEth serves as a sensitive marker of ethanol ingestion. There are several PEth homologs, PEth 16.0/18.1 is the most prevalent (37-46%) and has clinically established cutoffs. PEth has been noted relatively stable over RBC unit shelf-life (mean 17.3% decrement over 5 weeks of storage).

Given the prevalence of ethanol consumption in the general population, detectable PEth is likely present in RBC units collected from healthy donors. RBCs with high level PEth could confound PEth testing in RBC recipients. Here we show the prevalence of detectable PEth in RBC units and report a novel finding, two patients with undetectable PEth pre-transfusion, which became positive after transfusion with a single high PEth-positive RBC.

Study

Design/Methods: With institutional review board approval, patients admitted to a single, academic, tertiary-care facility receiving a single RBC transfusion in the prior 24 hours were identified. Segments corresponding to transfused RBCs and recipient pre-/post-transfusion ethylenediaminetetraacetic acid/whole blood (EDTA-WB) specimen pairs (collected within 28h transfusion) were tested for PEth 16:0/18.1. PEth testing was performed via a laboratory-developed, LC-MS/MS assay that quantifies PEth 16:0/18.1 on a Waters XEVO TQS instrument (Milford, MA) using PEth 16:0/18.1 D5 (Cerilliant/Sigma-Aldrich, Burlington, MA) as internal standard. The assay has a lower limit of quantification of 20 ng/mL and a coefficient of variation of < 10%. PEth normal, moderate and high levels were < 20, 20-200, and >200 ng/mL, respectively. For determination of recipient pre-/post-transfusion PEth delta, all PEth results < 20 ng/mL were deemed 20 ng/mL.

Results/Findings: 62/151 (41.1%) segments were PEth detectable (31.8% moderate, 9.3% high, Figure 1A). Among PEth detectable segments, mean (SD) PEth was 144.9 ng/mL (224.9, Figure 1B). In 5 pre-/post-transfusion EDTA-WB pairs, pre-transfusion PEth was undetectable in all samples. Transfusion of RBCs with 109.7-324.9 ng/mL PEth produced no detectable EDTA-WB PEth increase (n=3). Transfusion of RBCs with 513.8 and 990.7 ng/mL PEth produced detectable EDTA-WB PEth increase (0.6 and 101.6 ng/mL, respectively). While 0.6 mg/dL is within the analytical variation of the assay, 101.6ng/mL is above it.

Conclusions: Prevalence of detectable PEth in RBC units was 41.1%. Two patients with baseline undetectable EDTA-WB PEth were PEth detectable after transfusion with a single high PEth-positive RBC. Notably, many solid organ transplant programs exclude PEth detectable patients from organ transplant due to concern for ethanol use/abuse. False positive PEth due to transfusion may, without warrant, preclude organ transplantation.