To address the biases associated with self-report, several alcohol biomarkers have been evaluated to objectively assess alcohol use.22 Phosphatidylethanol (PEth) is a direct metabolite of alcohol consumption formed from phosphatidylcholine by the action of the enzyme phospholipase D, and can detect alcohol exposure up to three weeks following consumption.22–25 PEth performs relatively well compared to other established alcohol biomarkers because it is both highly sensitive (ranging from 85% to 99%) and specific (almost 100%).26,27 It does not appear to be affected by age, sex, other ingested substances or non-alcohol-associated diseases.24 However, it can vary between persons consuming the same amount of alcohol, likely due to differences in alcohol metabolism.28 In settings in which under-reported alcohol use is common, the high specificity of both PEth and self-report have been used in combination (considered positive if positive on either measure) to increase sensitivity.29
