Characterization of phosphatidylethanol blood concentrations for screening alcohol consumption in early pregnancy.

Objective: Phosphatidylethanol (PEth) is formed endogenously by the direct action of ethanol, and has a half-life long enough to make it a reliable biomarker of alcohol exposure in early pregnancy. In this study, we aimed to characterize PEth blood concentrations to differentiate different levels of alcohol exposure in pregnant women.
Methods: The study consisted of 305 consecutive pregnant women who had been referred to our hospital for antenatal care. Of them, 117 self-reported alcohol ingestion in the first trimester of pregnancy and 188 were abstainers. Total PEth concentration in whole blood was quantified by liquid chromatography-mass spectrometry (LC-MS/MS). Alcohol ingestion was classified according to the United States National Institute on Alcohol Abuse and Alcoholism into light drinkers: ≤ 3 drinks/week, moderate drinkers: 3-7 drinks/week, and heavier drinkers: > 7 drinks/week (a standard drink = 14 g of ethanol).
Results: Participants had quantifiable PEth blood levels 3-4 weeks after the last drink. There were 4.8% abstainers who had positive PEth concentrations; all of them reported a positive history of alcohol consumption before conception. PEth blood concentrations were significantly correlated to drinks per occasion (r = 0.44; P < 0.001) and days drinking per week (r = 0.34; P < 0.001). However, almost 74% of participants with ≤ 3 drinks/week of alcohol, and 46% with 3-7 drinks/week, had PEth blood concentrations below the lower limit of quantification (LLOQ). The area under the curve (AUC) generated by a receiver operation characteristic curve (ROC) analysis increased as the cutoff value of PEth blood concentration increased. However, the cutoff values were below or close to the LLOQ.
Conclusions: Our study presents a formal characterization of PEth blood concentrations for screening alcohol ingestion in first-trimester pregnant women. However, caution is recommended for overrepresenting either negative or positive results.