Dose–Response Characteristics of the Alcohol Biomarker Phosphatidylethanol (PEth)—A Study of Outpatients in Treatment for Reduced Drinking

Abstract Aim Measurement of whole-blood phosphatidylethanol (PEth) offers high sensitivity and specificity as alcohol biomarker. A remaining issue of importance for the routine application is to better establish the relationship between PEth concentration and amount and duration of drinking. Methods The study included 36 subjects (32–83 years) voluntarily attending outpatient treatment for reduced drinking. At ~ 3- to 4-week intervals, they provided a diary on their daily alcohol intake and gave blood samples for measurement of PEth and carbohydrate-deficient transferrin (CDT). Whole-blood PEth 16:0/18:1 was measured by liquid chromatography-tandem mass spectrometry and serum CDT (%disialotransferrin) by high-performance liquid chromatography. Results At start, the self-reported past 2-week alcohol intake ranged 0–1260 (median 330) g ethanol, the PEth 16:0/18:1 concentration ranged 0.05–1.20 (median 0.23) μmol/L, and the CDT value ranged 0.7–13.0% (median 1.5%). At the final sampling after 5–20 (median 12) weeks, neither reported alcohol intake nor PEth and CDT levels differed significantly from the starting values. The PEth concentration showed best association with past 2-week drinking, followed by for intake in the next last week. The changes in PEth concentration vs past 2-week alcohol intake between two successive tests revealed that an increased ethanol intake by ~ 20 g/day elevated the PEth concentration by on average ~ 0.10 μmol/L, and vice versa for decreased drinking. Conclusions The PEth concentration correlated well with past weeks alcohol intake, albeit with a large inter-individual scatter. This indicates that it is possible to make only approximate estimates of drinking based on a single PEth value, implying risk for misclassification between moderate and heavy drinking.