¹Neuroscience and Physiology, Psychiatry and Neurochemistry, Gothenburg, Sweden, ²Karolinska Insitutet, Department of Clinical Neuroscience, Stockholm, Sweden

Background: Phosphatidylethanol (B-PEth) is an objective, quantitative alcohol blood marker, with 100% specificity for alcohol, accumulating in red blood cells at alcohol intake and typically used to detect individuals with repeated frequent drinking over time, as well as for monitoring its elimination after abstinence during treatment for alcohol use disorder (AUD). The slow decline of whole blood PEth, with an elimination half-life of almost a week, is the foundation for its usability as a cumulative biomarker of recent alcohol consumption.
Traditionally, B-PEth is analysed on venous blood samples. However, the need for collecting venous blood samples may be a limiting factor in many instances. With new technology B-PEth can be analysed on capillary blood with the dried blood spot method (DBS).
Establishment of dried blood spots (DBS) as a specimen for PEth determination offers several advantages. An easy-to-use blood biomarker to correctly assess alcohol consumption is an invaluable asset in alcohol treatment strategies, as well as in alcohol research studies.

Aims & Objectives: The aim of the study was to validate the use of the volumetric technology and the accuracy of determination of B-PEth concentrations compared to venous blood sampling.

Method: Blood sampling from 48 AUD patients undergoing alcohol withdrawal treatment at the Dep Addiction Disorders, Sahlgrenska University Hospital, Gothenburg Sweden, was performed ones or twice (n=33) with quantitative DBS (qDBSV) device, venous blood on qDBSV and liquid venous blood. Samples were stored in -20 degrees and analysed with liquid chromatography tandem masspectrometry ( LC-MS/MS) developed at ABC labs, Stockholm, Sweden.
The blood sampling used a commercial volumetric DBS device having a phosholipase D inhibitor incorporated to stop continuous PEth formation.

Results: An LC-MS/MS method for measuring PEth with volumetric DBS was succesfully developed and validated. The method quantified PEth in the range of 0.05 – 10 mol/L, with a bias and imprecision of less than 15%. The method validation showed precise and accurate results in an AUD population with capillary and venous blood DBS analysis showing r2 of 0.963.
The presence of an PLD inhibitor prevents post-sampling PEth formation. Also, drying time of DBS beyond 3h showed no difference in results.

Discussion & Conclusions: This study demonstrates that volumetric capillary DBS is a valid alternative for measuring B-PEth concentrations in blood. The DBS method does not require sampling at health care settings and thus presents an easy and less invasive way for determining B-PEth and new possibiliteis of monitoring alcohol consumption and treatment effects. With DBS sampling offers solutions as home monitoring and easier access for patients in rural areas as the DBS can be stored in room temparature and mailed.
Also, in this study a device with volumetric design was used to provide a precise blood volume for analysis and a Phospholipase D (PLD) inhibitor is present in the device to prohibit post-sampling B-PEth formation, providing further accuracy to B-PEth results.