Phosphatidylethanol: The Potential Role in Further Evaluating Low Positive Urinary Ethyl Glucuronide and Ethyl Sulfate Results

Background Whereas urinary ethyl glucuronide ( E t G ) levels above 1,000 ng/ml reflect with a high probability ethanol ( E t OH ) consumption, levels below this cutoff are difficult to interpret as both extraneous (nonbeverage) E t OH exposure, recent drinking, and more distant high E t OH intake (several days ago) might yield similar results. This might be of particular relevance in medico‐legal cases. To overcome this dilemma, phosphatidylethanol ( PE th) might be a promising marker, because blood PE th is only positive following significant alcohol use. The aim of our study was therefore to employ PE th as a marker to differentiate between the different conditions. Methods Subjects included were 252 participants in monitoring with the A labama P hysician H ealth P rogram. All subjects testing positive for E t G and/or ethyl sulfate ( E t S ) who denied drinking after routine supportive confrontation were subject to information about PE th testing. If they still denied drinking, PE th testing was performed and the result communicated. E t G , E t S , and PE th testing was performed in a commercial laboratory using liquid chromatography tandem mass spectrometry methods. Results Of a total of 18 subjects who tested positive for E t G and/or E t S , 10 denied drinking. Of the 7 who denied drinking after PE th explanation, in 5 cases, their claim was supported by a negative PE th result. In 2 cases, a positive PE th result was in contrast to their claim. Conclusions PE th results in combination with previous low positive E t G / E t S results allow differentiating between innocent/extraneous exposure and drinking. Negative PE th testing following low positive E t G / E t S results helps to further elucidate the findings and support the claim of the patient of recent alcohol abstinence. Positive PE th testing following positive E t G / E t S results confirms recent drinking.