Assessment of Clinical Ordering Practices of Phosphatidylethanol Monitoring for Alcohol Use at a Large Academic Medical Center
Authors: Herb Thomas , Gherasim Carmen , Manthei David 
Published: October 2021

Abstract

Objectives
Phosphatidylethanol (PEth) has emerged as a specific biomarker for alcohol use with superior diagnostic values compared to traditional alcohol biomarkers including urinary ethyl glucuronide (uEtG), urinary ethyl sulfate (uEtS), and carbohydrate-deficient transferrin (CDT). PEth can extend the detection window of alcohol use up to 28 days and has been dubbed a “hemoglobin A1c”-like biomarker for alcohol use. Measurement of PEth concentration in the blood has become of increasing interest in a wide variety of clinical settings including transplant evaluation, detection of chronic alcohol consumption and monitoring alcohol abstinence. Availability of PEth testing is currently limited to few reference laboratories; at our institution, PEth quickly became one of the most expensive chemistry/toxicology sendout tests. Few testing guidelines exist for PEth regarding test utilization and time intervals for appropriate repeat testing. This retrospective analysis was conducted evaluating the patterns of PEth ordering to inform best test utilization strategies.

Methods
A retrospective limited data set of PEth (PEth 16:0/18:1 by LC-MS/MS) test results was obtained from a large academic medical center. Concordance of the positive test results using a cutoff of 20 ng/mL for repeat testing within 7, 14 and 28 days was analyzed.

Results
3,739 distinct results from 1,957 patients was obtained. The median age of patients was 57 years (range 19-94). Males accounted for 58.4% (1,142 patients) of the testing. The overall positivity rate was 23.3% (median concentration 188.5 ng/mL), with 52% of positive results suggesting moderate alcohol consumption (20 – 200 ng/mL) while the remaining 48% reflected heavy alcohol consumption or chronic alcohol use (&gt;200 ng/mL). 588 patients (30%) had multiple PEth results, including 150 patients with ≥ 5 results and 36 patients with ≥ 10 results. Long term monitoring of alcohol use in pre- and post- transplant patients (n=36) with ≥ 10 results revealed that 52.7% had all negative results, 5.6% all positive results, and 41.7% with mixed results included a subset (25%) initially positive and subsequently negative results monitored for up to 2 years. Analysis of two consecutive tests ordered within 7 (n=96), 14 (n=205) and 28 days (n=411) revealed that 90%, 82.9% and 83.7% of the results had the same interpretation with an average change in concentration of 15.2 ng/mL 35.9 ng/mL, and 35.4 ng/mL, respectively. Of the 10% observed changes within 7 days, the majority accounted for expected PEth 16:0/18:1 elimination.

Conclusions
Our data suggests that long-term monitoring of alcohol use with PEth may be helpful in the surveillance of alcohol abstention or alcohol relapse that can assist in prioritizing patients for liver transplant. To improve PEth test utilization (and decrease expensive sendout testing), PEth should not be ordered less than 7 days apart. Instead, recent alcohol use may be monitored with traditional biomarkers (uEtG/uEtS).