Device does matter! Comparison of PEth 16:0/18:1 and PEth 16:0/18:2 blood concentrations determined from three dried blood spot sampling devices

The biomarker phosphatidylethanol (PEth) can be determined in whole blood to distinguish between alcohol abstinence and alcohol consumption. Routine analysis is commonly performed using dried blood spots (DBS), as PEth is considered stable for extended time periods in this matrix. However, the coexistence of many DBS devices, coupled with insufficient data regarding their comparability of results, pose a major challenge in forensic and clinical practice. We therefore analysed and compared blood samples using three DBS devices commonly employed for PEth testing (Whatman™ filter paper, Mitra® and Capitainer®B Vanadate). PEth 16:0/18:1 and 16:0/18:2 were extracted from DBS using a water/propan-2-ol mixture and subsequent liquid-liquid-extraction using n-hexane. Analysis was carried out via LC-MS/MS. Ethanol and acetaldehyde concentrations were determined in each blood sample via GC-FID. A total of 100 blood samples were analysed, of which 76 were found to be positive for PEth. These included 24 cases with PEth concentrations < 20 ng/mL, 43 cases with concentrations ≥ 20 ng/mL to < 200 ng/mL and nine cases with concentrations ≥ 200 ng/mL. The Mitra® and Capitainer®B Vanadate systems resulted, on average, in higher PEth concentrations compared to Whatman™ filter paper. The percentage deviations ranged from -8-116 % for PEth 16:0/18:1 and from -14-264 % for PEth 16:0/18:2. Ethanol and acetaldehyde above physiological concentrations (1.42 g/L and 0.727 mg/L, respectively) were observed in one case only. While DBS are a reliable method for PEth analysis, the choice of device can influence results and potentially impact interpretations of alcohol use and abstinence.